I think you'd find yourself quite happy with about 100 flywheel horsepower from the A15. It could be done with a change of camshaft, fitting of a downdraught twin barrel weber, a slight increase in the compression ratio & the fitting of a good set of extractors & exhaust. You wouldn't have to overbore the motor, though a clean up of the bores 0.5mm may be necessary. This is the recipe I have for my Sunny wagon with an A15. It has 300,000 k's on it, & when I finish putting the L20B into my Sunny coupe, I'll probably pull the engine out & get it rebuilt. The car is already quite nippy with the A15, surprisingly more so than the A12 powered Sunnys I've had. So, a factory 70 degree cam with GX valve springs, 76.5 mm stock replacement pistons, a 32DGV or 32/36DGV Weber, a factory GX exhaust header or aftermarket extractors, a larger exhaust, an N12 Pulsar electronic distributor & a HEC715 coil to suit is what I want. If you still want more power, twin sidedraught carbies, larger camshaft , bigger pistons etc,can be fitted. I'd recommend you fit the A15 first, to see how much more you need after that. Remember, the A15 is already 86HP, with a lot more torque. A bit of fine tuning & you could be very happy with the result. My second 1200 sedan had 100 HP at the flywheel, & it was a rocket, so 90-95 might be just what your looking for. Good luck as always with what you do, let us know how you're getting on, too. Too many times I've never heard from somebody again, I always wonder was what I said any use. So I hope this is useful to you.