If they are d2ve's sorry to say they are open chamber junk, you will have a motor that will ping because you cant get the quench area where it needs to be with those heads. You still have an intake? if you have the stock iron cj intake it is a good piece. If you can find a set of c8, c9 or d0 heads get a good valve job on them and with a trw replacement piston you have about 10 to 1 comp ratio.
A nice hydraulic cam, recurve the dist and put an 850 on it and you will have a great motor that will last. Yes there are diff clearances and you should do a little work to the brgs. Get ahold of lakes only or 058 and they can give ya tha skinny on where to set up the clearances and I am sure lakes will have some more to offer. Btw, isky makes an nice cam for the 460 for marine use.