would stay low rev as you mention. There are a lot of aftermarket cams these days with strong low end. The thing to keep in mind is more cam will most likely have even less bottom end torque - IE less likely to do a burn out.
So maybe you need something a little similar to an RV cam or a 1/2-3/4 ton truck cam. Short duration very low overlap and maybe faster ramp speed with a little higher than stock lift. Not to much cuase then you get into valve spring issues, piston clearance etc...
This will keep your engine in the 1200-4500 peak power range. Anything more will hurt the stock compression and the low end pulling power.
I also see where you are coming from too, I would not spend to much money either if you are swapping engines etc. The 318 would also like a little more carb, better intake and of course better exhaust too. But I would just patch it until I put the new engine in if I were you..:supz: