I am building two motors they are 468 cu in they are 8:1 compression dart pro one aluminum head 310 cc Coustom c to match b&m 250 blower with 6# of booste how much horse power do yor think it will make

550-570 hp depends on cam profile

Thinks I am getting with a camotion on cutting a cam

Exhaust, and cam specs?

I'll say 600-650 with a good cam. Considering, a 525sc plus better heads, bigger blower, more compression, and assuming you use a better cam.

hard to say , 675ish with those heads, and a good cam, single or dual carbs?

600-625 hp would be my guestimate

Dual carbs header

625

My guess is 600HP. I would caution about going any higher than 6 lbs with that 250 blower. It will heat up the intake air temp and cause detonation which will kill a boat motor quickly.