16v redtop is really the best conversion for your money. You can pic an engine up for next to nowt these days and it dont cost £500 for shafts and hubs............infact you could probably do the full conversion for that if you done it yourself. As for the grip probs,using an f20 i'd jusy band a quaffie diff in there,job sorted. If you dont want to fork out for a diff then equal lenght shafts and decent tyres.
My old nova(LET) ran 250@wheels and grip wasnt that much of an issue tbh, i think alot of people just dont spend the little extra that makes all the difference. However with fwd there comes a point where its just beyond a joke but i dont think you'll get anywhere near tht with N/A.