Assuming they are 215 or 225 hp models, you should cruise at 22-25 mph, and WOT should be 30-35 mph, depending on a bunch of different factors. If they were the 240, 275, or 300 hp models, you'd go a bit faster. The 360ci was even available as a 340 hp inboard in 1971-72, using roller rockers and a high-lift cam.
You can get Chrysler marine 360 long blocks from
California Engines for $1300 plus core and shipping.
__________________
Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury