79mm pistons will give you 1608cc on an A15.

At least among the racecar set, the 79mm bore size is relatively common, but as has been said, racers are obliged to regard the block as just another consumable.

For street use in an A15, I personally recomend the second oversize of 77mm. This allows ready availability of both factory & 'replacement' pistons & rings & compression ratio's that can live with pump fuel.

This also allows for one more bore job in the event of high mileage wear or some mishap with a broken ring or dust ingestion.

For mild street engines, the smaller bore size will not be a handicap, but for a full blown race engine, well that's a different story.

yes I have an a14 with an a15 crank sitting in the shed thats going to go into the old beige sedan when it goes back on the road. It'll be 77mm bore with probably a factory 70 degree cam & a baby weber off a 1600cc escort (32dfv). This will give me another 2 overbores at 77.5 & 78 mm.Built right the first time it should last a few years, then with 2 other rebuilds it should outlast me. This is the engine i use to race in the biege sedan, & we used a14 pistons machined to slightly below deck height & it still pinged like a beaut on 98 octane fuel. Needed avgas & twin webers to cure that problem. it still killed the engine later, because we found bits of piston ring in number 1 cylinder. Problem was the ring was from number 3 piston, which was very melted. Pinging is called the Hiroshima Hammer Dance cause it's pounding the crap out of the pistons, rings & Block.