225 rebuild advice

You might take a look at some of the engine builds over at slant6.org and do a lot of reading both here and over at .org. That said, I would up the compression ratio by either decking the block and/or the head (measurements for chamber volume, pistons below the deck, etc are important here). Nothing too radical on the cam. I would most probably go with a Super Six 2 barrel set-up and a larger exhaust than stock. Just these mods will wake up the slant quite a bit.