i know the A15 in my sunny sedan is 78.85 mm bore with a stock stroke for 1598 cc's. So you don't need a offset stroke the crank. If you did you'd be in the middle of the 1600-2000 class, & it'd probably be best to start with a 2 litre engine if you wanted to be there.

So my recommendations would be 82 mm stroke, 78.5/79mm bore, get the block bored out by a reputable race engine builder, not an engine reconditioner ( i suffer from a badly balanced engine because i made this mistake). Get the Crank cracktested, & if it passes get it nitrided, because they live longer that way.The first a15 i bought was somebody's old race engine & it was cracked in all the journals.

try & find some guys running speedway with a series engines, & see if they can recommend cam grinds, as they need both torque & horsepower from their engines, & an engine that has power below the line is better than an light switch engine. Use the stock rods but get them shot-peened & beam polished, & use the ARP rod bolts. Get it balanced properly, including the front pulley, get a new oil pump as they're still available, use good quality twin valves springs, you can get l16 valves cut down & new valve sets fitted, but you need lash caps as the valves themselves will wear as the ends aren't hardened any more (personal experience again). Get a good Distributor for it, N12 electronic can be fitted, Somebody has used l series electronic, or an RX7 crank sensor has been fitted by someone if you want to use an ingition computer. DCOE Webers (40 or 45 mm) or Dellorto's, or throttle bodies from various manufacturers can be fitted. If you've already got webers, use them.
Do a light clean up on the head, but don't go to far to start with. I know some engine builders claim bigger is better, but i personally disagree. I've read in 2 books about Coventry Climax race engines about how sometimes their engines came back for a rebuild with less horsepower than when they were sent out, because some teams would port them out, notably Lotus & Stirling Moss.

Put a good set of extractors put on, Liverpool Exhaust here in Sydney have off the shelf, mandrel bent sets for A15's into 1200's, & a 2 inch pipe with a small flow-through muffler & out the side just in front of the rear wheel.

Don't forget fuel supply, get the outlet on the tank enlarged to at least 8 mm, use a good electric fuel pump & change the hard line under
the car to a minimum of 8 mm as well. that way there'll be enough fuel at the top end, which is sometimes a problem.