try this website for carb info
The Hitachi-SU Tech Pages
lots of good info here

actually, I have 2 of them.
problem is that I'm here and your there.
Oz is a long way from the Stone age (Utah)

what is your initial timing set at? how quick is your advance curve? what grade of fuel are you using? what plugs and heat range are you using? is the cam timing advanced?

it sounds to me that your spark plugs are the wrong heat range and retaining too much heat in the combustion chamber, or possably thhat your advance curve is too quick there by causing preignition, or maybe a combination of both.

SIMPLE, use L28 Turbo pistons from an 81-82 280ZX, std. size for them is 86.00 mm where as standard bore for an L20B is 85.00 mm. Obviously your block will need to be bored, but other than that it's a straight bolt in item, this should net you between 8.0 and 8.5 compression ratio.

looks like an MGB, but I can't say for certain

saw this done back in the early 1980's, a guy came into the dealer and wanted a tune up, the service writer couldn't believe that an owner of a british car wanted a Datsun dealer to tune up his car. until he opened the hood. same said service writer used to work for the British Leyland franchise down the street.
the cool thing about it was/is that if it wern't for the name DATSUN on the valve cover, no one would have been able to tell that the engine had been changed, it looked like it came that way.
in talking to the owner, he said that there was double the power, twice the gas milage and NO repairs to speak of
that motor and trans came out of a 1976 B210

first, drain the coolant. then replace the bad head gasket. once the engine is reassembled, drain the oil pan. this will get most of the junk out. refill with new oil and change the filter. fill cooling system with water then start the engine and allow it to warm up with the radiator cap off. when the engine is at normal operating temp., turn it off and adjust the valves. add a cooling system cleaner to the radiator, set heat lever to the hot setting, then restart and allow to run for the time specified on the cleaner container. once it has run for the required time, turn off again and drain the cooling system. refill again and run for about 5 minutes and then drain again. this should get the junk out of your cooling system, then refil with a 50/50 mix of water and coolant. once that is done, change the oil and filter a second time and you should be good to go.

the H72 head casting number means that it's a standard A14 head, the GX head for an A14 should be a H57 casting number and will have small water holes under the intake ports.

use this; [/url]www.gt-racecar.com

you need to find a dealer who has some oldtimers
IF I remember correctly, the aluminum housings were used in the roadsters (SPL/SRL311), and yes they are different than the later ones.
the best that I can offer right now is this, after the weekend I'll go visit the dealer I used to work at and get you more info, but it's going to take a few days

"R" series diffs. are for independent rear/front suspension.
"H" series diffs. are for solid rear axle rear suspensions.
the number, as in R160, is the inside diameter of a given ring/crown gear.
from what I remember from my time working in a dealer, there isn't much interchangeable between the 2 types. maybe small parts and some bearings.
it would be kinda hard to fit a 160mm gear to something designed for a 165mm gear.