Olds 307 to Olds 403 engine swap info please?

Here in Ontario, if it had a cat when new, it has to have one now, period, smog test or not, and Nora always had 2. You will find that if you go to a full, true dual exhaust it will run better and get better mileage than a single with a Y. Just make sure you use an H or X cross over. That does fit under these Cutlasses, because I've seen my exhaust guy do it.

 

To do true duals I'd need to either notch the transmission crossmember or replace it with a custom one. To stay conpliant for inspection I'd have to have dual cats. It's just too much money. Will be doing a single new free-flow cat, y-pipe to two Turbo mufflers, and exhaust out like stock 442/Grand National behind the rear wheels.