a15 is 80hp at the engine so an extra 20hp is possible but youll
need rpms and bigger valves also unless you want to rev sky high.
Its going to be hard unless your camshaft is a little more serious.
Also if you are going to rebuild her with a late a15 crank,
77.5mm slugs and total seal rings once you up the comp to 10:1.
Maybe 44mm sus will also help compared to 38mm hitachis.

Otherwise simple ST turbo with SU for 100atw at halve the cost.