In NSW it used to be & still could be that the widest wheel for a car under 1000 kg was 6 inches. The heavier the car, the wider the wheel could be. It had nothing to do with whats on the tyre placard, as most insurance companies will try & tell you. The 1200 came standard with a 12x4 inch wheel so we'd all have to find 5 inch wide wheels. I think you can get them engineered with wider wheels, but it's up to the engineer & you're stuck with that size unless you want to re-engineer the car. If you're putting an SR20 into it, surely you've talked to an engineer. I'd suggest you give that engineer a call & ask his opinion. A 6 or 7 inch rim with some 185-195 wide tyres has plenty of grip. Another thing that I found out is that the wider the tyre the less weigh there is on the contact patch of each tyre & the less grip you get, & the more likely it is to aquaplane in the wet. I've run 175/60 x14's on 5 inch steelies as wet weather tyres before, as well as 185/60x13's on 6 inch rims. This allowed for good grip & good wear. I seemed to always get 2 years running out of a set of tyres. Even when I was delivering pizza's I'd get 12 months worth from the Sunny I had, with some 195/60x14's on 6 inch rims. I reckon the 14x6.5's you've got with some 205/55x14's would be a good thing, because of the extra weight of the car after the engine swap.