What overbore needed for 1500 spitfire?

[hardhatharry]

I have pulled out of the scrap pile the engine we will call superfast engine no 1 for the 1500 spitfire. Piston / bore is a bit worn so needs oversized pistons and a rebore. The largest bore is 74.62mm what oversized pistons should I buy for the minimum rebore I can get away with?

[Clive]

Let your machine shop advise you. They will measure the bores and should be able to get the pistons too. Then they will bore to suit the actual pistons, I have it on good authority some "sets" of pistons vary in size, so will be marked so you fit them in the correct bores (I had county pistons, and they were all identical)

If building a fast road 1500, the important bit will be the crank and big ends. And getting it fully balanced (even then mine lost a big end at goodwood at a mere 6000rpm)