Simon is on the money.

With regard to port matching, and opening up the oval port heads in general, it starts (for streeters) with getting rid of the weak links. If the valve diameter is enough to support 150bhp (for example) and the 'main' straight section of the port flows enough to support 160bhp or more, then going much larger on valve size (at this stage) or main port size just won't return any gains. what it might in fact do is drop velocity and reduce mid range torque, with no gain up top.

THe vast majority of the work has to be around the valve/seat area and teh valve guide area, the bowl (the port area around the valve seat) and the short turn radius. For a streeter, you realistically won't need (or want) to touch the main port straight sections at all.

In terms of port matching, get them 'close' but leave it (if material permits) with the intake manifold runner exits being about 0.5mm smaller than the head port entry. This won't affect flow in teh 'right' direction, but that tiny step will help work against flow 'reversion' (flow trying to go in the reverse direction). This won't add power at peak rpms, but down lower where longer cam duration adn later intake valve closing leads to less output (less cylinder filling due to some intake reversion) well that 'step' can help a lot. On a cam that might otherwise not come into its sweet spot till (say) 3500rpm, you might be able to get it on song by 3250rpm. That doesn't sound like much but that is _massive_ on a streeter, esp with stock gearbox gear ratios where you have to hold a gear and drop the rpms lower than you might otherwise like to (since the next gear down has the engine screaming too much).

Do a bit of a search on google about 'dynamic compression ratio' which helps to explain the difference between static compression ratio as measured and what the engine will actually do in practice (esp at lower rpms). basically you tailor the cam and static compression ratio to one another, the bigger the cam, the more comp you can run on a given fuel (within reason, and remember you need more low-mid range output so going too big on the cam is not the answer, it's about a 'balanced' approach)

On which note (compression ratio) if it isn't a daily driver but more of a 'fun' streeter, depending on your local area, give e85 (or whatever the pump version is) a thought. Yes the pump fuel stuff will vary down to about 75% ethanol, but if you tune for e85 in general, you can run much much higher compression ratios safely, so you could go to a point safely lower than the max you could run on e85, but much higher than on pump 98 high octane, and be safe as can be even when the ethanol content is lower.

Let's say your engine combo with a particular cam will run safely on 98 octane with 11:1 compression. On e85 it might be able to run as much as 12.5-13:1 safely. If you went with 12:1 then even with less than 85% ethanol you'll be completely safe. And relatively cheap compared to 98 octane to fill up.

Yes the a/f ratio with e85 needs to be a fair bit richer, but the hidden plus is the considerable hike in compression ratio in and of itself produces significant gains in fuel economy, so as long as you don't get ridiculous, it will get enough fuel economy to do club runs and the like without too much trouble.

When it comes to NA power, yep, more capacity is almost always the go. However you can get to a point where with too long of a stroke, there's a lot more sidethrust on the bore walls when the crank is at about 90 degrees and the rod is at maximum angularity. This pushes against the bore wall in a sideways direction and will accelerate wear and compromise ring/bore seal. So you can eventually get to a point where you lose power. On a similar note, going too big on an overbore can bring in the same thing. This time not caused by increased rod angularity, but instead by a thinner bore wall more prone to flexing.

Absolutely if I was looking for some hypothetical 'best output from NA series no matter what' setup, then I'd be guessing that around 1650-1700cc (achieving as much as possible though boring and sleeving the block to suit the biggest bore I could fit, but knowing that boring that far just to fit the oversize sleeves will result in stronger bore walls but the block rigidity itself will start to be compromised a lot, so it won't be a 'long lived' engine) and achieving the rest via stroke increase - probably not beyond 84mm. The problem with all this is it won't be a practical or long lasting streeter.

So with all that in mind, a std a14 or a15 block (a14 if it helps with rego) overbored to the next size (just to clean it up, presumably it's a s/hand engine with miles on the clock so won't just freshen up with a light hone) and a15 internals would be 'the go'. Get the head 'pocket ported' (which is typically the name given to mods in the areas I stated above, and by the way this will get you about 85-90% of the flow that that head is capable of, from the first few hours of porting work. To get much more flow, you'd need probably 2-3 times as much labour time for just those few extra percent. Not justifiable on a streeter.

If you do go to e85 *(and this goes for normal petrol spec heads too, but even more so for ethanol since there's more fuel being fed in there for the same amount of air) make sure nobody polishes the intake ports, it'll gain nothing on a flowbench, and in practice the smoother surfaces encourage fuel to stick to the port walls a lot more, so rougher surfaces lead to better fuel suspension in the airflow, a more consistent distribution of fuel, and more consistent/advantageous combustion. win win, so to speak.