1. an oil plug (the kind with the square inset, on the rear of the block) would not come out and I tried various bolt extractors to get it out. It is almost drilled it out yet still enough remains to obscure all the threads of the hole, Should I a) finish drilling it out completely and then tap a larger diameter hole, e.g. to 1/2 inch, then use a 1/2 inch diameter, 1/2 inch long bolt to plug it? OR should I drill it out and use helicoil replacement threads, and then put a new oil plug in?

2. cylinder walls have a worn in ring around the top of the bore 1/4 inch from the deck. Is there an easy way to fix this at home or does this need professional machine shop to fix?

3. How do I remove wrist pins from pistons? (do not have retaining clips) tried heating rod and pin with a torch and then hammering with a rubber mallet.

4.what are the biggest bang for the buck things I should do to get to 250 HP? pistons, crank, cam, heads?

5. looking for a recommended setup for intake manifold and fuel delivery that will be legal in TX to replace a fuel injected engine from a 1991 vehicle.