988 cc's

Maybe:

Electronic Ignition

Mill the head down just a tad (you won't really need to as the KB10 had a slightly hirgher compression ratio A10)

Mild Camshaft

Quad Carbies or twin SU's

And then when that's all done you can start thinking about valve springs and some minor porting (or oval port head).

The A10 has the flat top pistons, lighter flywheel and the highcomp head (KB10) so it's a good starting point for a mild performance engine, plus the stroke is so much smaller so you'll get a very responsive engine with some relatively minor work.