The first thing I would recommend is changing out those 624 heads. They are extremely light 76cc castings and make excellent doorstops.

I have Vortecs on my 406, with Comp's XE268 cam. I went with slightly dished pistons to get the static compression down to 10:1 with these 64cc heads. This combination would break the tires free even with the old 2.41 rear gears I had.