small block cams

I don't know on convertor brands personally. We have a place here that we like, will rebuild or build a custom one for a reasonable price. Others probably have preferred brands they can recommend.

Not sure on that either, there's charts on the web, just google for mopar axle housing sizes. Any A-Body 8-1/4 should bolt in I believe but the housing I think will always be wider than a 7-1/4 so make sure your wheels will still clear everything. You'll also need to shorten the drive shaft when going to an 8-1/4 and even shorter for an 8-3/4.

The 7-1/4 sure grips are hard to come by. Not many people want them but they are worth money when you find the right person. If you get it dirt cheap or free, I would be inclined to sell it for a profit and use that dough to buy a ready to run 8-1/4. I got one of those once for $400, complete with sure grip, 4.56 gears, brakes, everything ready to go.

On the pistons, I think the ones guys here like are Keith Black 167 (as noted by Lelo Dart below)? Double check that but I think there's only one that will get you that compression. If you do go that route, you'll have more options on viable heads I think. That being said, I don't think I'd invest money in machine work and a real rebuild on a 318. That stuff costs the same on a 360, and if I were building an engine I'd go bigger. I paid $500 for my fairly fresh 318 with carb, trans, etc. After ditching the parts I didn't want, the cam swap and rebuilding my original 273 heads I have about $1500 in the engine which is far cheaper than I could have build it from scratch for. Bargain is what this engine is all about.