I'm not familiar with that version, but the math works for 1.6 and .509 cam. My experience with crate engines is, MP shouldnt be involved with them. I wouldnt blame the previous owner totally. Cummins isnt the best at weeding out problems before they get shipped. If it were me, I'd have every dimension checked, assume nothing. Common issues are problems with the rod sizing, wrong bearings, I've heard of pistons not having any rings at all on one piston. It would surprise me if the ring gaps are even close and the bores arent finished to proper finish and size. On the heads, the Stage VIs had some serious casting issues, and the valve job is one of the worst. Seats out of round, valves sunk, guides too tight. Have everything checked. The crate engine program is still in the 50-60% good, with Hemis and big blocks being the worst. I wouldnt even try to run a new hemi without taking it all apart and starting from a clean block. They are the cheapest way to get all new parts tho. As far as a cam choice, a ".509" in that engine is a mild cam. I dont think it would make the power advertised tho. Most dont. A 500" engine with the long stroke will eat up a cam's duration, and a carb's cfm rating. As far as cams go, I'd lean this way...Crane makes some very strong hydraulics. They are split pattern, and are easy on springs. The first p/n 684561 made 470tq to the tires at 3700 rpm in a 10.5:1 440, idles clean at 800rpm, and pulls to over 6500. The second is it's bigger brother, p/n 684571. I have a 440 going together with the bigger one right now. You may need new valve springs with both of these. They require doubles, and the heads may need to have the guides cut for the small positive seals. Thesse cams in a 500" engine will be very strong, and still idle well. I would expect the hp to be higher too if the heads flow what they are supposed to when they are fixed.
