360 smogger or not??

Good idea on the intake spacer and milling the heads.

As far as converter like Rumble said you really need to know what cam you have and match the converter to it and the weight of your car and gears and tire size. All makes a diff. I can say thought that if the cam idles smooth you won't need a very high stall. As far as what to do with the 904 if it works fine I'd just add a Trans-go TF-2 kit to it. That'll make it shift nice and firm. The 904 is a pretty tough little bugger when in good shape and having a TF-2 kit.