4.6 bore 4.5 stroke, Big M block with splayed mains(just in case you upgrade HP later). I had good luck with the callies and Oliver's as well. Most of the head companies have a good CNC version head, I like the brodix 3X CNC, I ran a crane hydrolic with .630 lift.I think. This should be a very user friendly package and have a long life.
Good Luck
Michael

Ive been thinking about doing the same thing. Will all of the accessories work going from a gen6 to a merlin or dart block?

mounting locations are different on alot of the items. That's one reason I stayed with a gen 6 block. (since I changed EVERYTHING else during the build)

heads I would buy from JIM V on the board I'll look for his # 10.2 big m block dart single plane intake match to heads jim can do that nickerson can set up the rest carb and motor cam I have a isky hdy roller have to find paper work but its like 622ex 617int 254 245 at 114 made 647 at 6000 with a 850, with the nickerson 1050 add 20hp that was a 9.5 to 1 509 Jim Reid was the builder he built a couple of 598s with just over 800hp at $16,000 he builds for boats,race cars also been around along time. I had him do the 509 then added the nick 1050, now looking for another 30 to 40hp so jim v comes to mind head work on boat motors is not the same as car set ups. jim the best so I MIGHT SEND HIM THE HEADS INTAKE TO MATCH AND MARK OUT THE EXHAUST SO HE CAN MATCH THAT. I will stick with Jim Reid I think for motors I HAVE USED HIM IN 3 BUILDS SO far in 12yrs . hes close are you going to put this together yourself or looking for a built motor. art

JIM VALAKO RACE HEADS 616 889 0928 HE can set you up with the heads flow them. hes the best in the us from what I have heard.like I said I am going to use him this winter. art

I want to put things together myself. I really enjoy working with motors and want the satisfaction or agony of defeat.

That depends on how long that you would want them to last!!!

Why not just buy world products engines, 632 ci?

598", 622", or 632" NA will easily get you 800hp on pump gas. Go with Dart 355 CNC heads, single plane with 1250 Dominator and large hydralic roller or relatively small solid roller depending on what rpm you plan to turn and if you want closer to 900hp. 598" is a great motor without all of the clearancing requed for the 4.75" stroker of the larger engines.

If you go blown you can easily get 800hp from 509" motor with stock Iron heads, hydralic roller, 8-71 blower turning slow...a chiller is not even necessary. better heads...more power and even safer....it all comes down to if you want to utilize some of what you have, or start completely over....

konrad 800 rtech package w/ warrenty