g'day .... just thought i'd throw in m 2cents worth as i've spent the money on an A12 and can vouch for their go this is what i started with ......
full balance - pistons, rods, pulleys, crank, lightened and balanced flywheel, GX kidney chamber head fully rebuilt with new valves, double springs and guides, ports and clean up, 9.8:1 compression, clives cams grind 82 (0.050" lift) with twin hitachi (su) carbs trumpets and sox and 4-1 extractors with a single free flow muffler (not even a chrome tip)

scince then i've upgraded to electronic dizzy(bluebird) high output coil and quality leads, twin 40mm webers(30mm chokes).
i've recently had it on the dyno and its putting out around 100hp at 6000rpm, revs out to 8500 without a drama and still has pull, and completely drivable on the street in traffic and on the freeways. all up i reckon i've spent near on $4000 give or take a couple hundred and i'm real happy with what i've got

i've also had a similar A14 and the biggest thing i can say the difference was is wheel spin .... A14'd spin thru 2nd and chirp 3'rd no probs and had a little more pull - A12 doesn't come close but seems to run better thru the entire rev range

either way you go i don't think you'll be disappointed .... good luck