360 budget build questions.

If you have the talent/know how on balancing rods, your in good shape. I'd skip OEM slugs. IMO, A New set would be the best ideas. Lighter weight and stronger. Like KB HyperU's. It also beats milling the heads a lot! (Same with the rods but there a bit pricey compared to $30-$40 OE replacements.)

Find a 8-1/4 rear at a min.