Howdy, Being as I am a marine diesels mechanic (working on Detroits and the occasional Cat in workboats) I was becoming impatient with all of the, ah, automotive style BS that is attached to my 6.2L 1983 Jimmy and was thinking of repowering... (that is to say, I'd like to do away with glows and much of the electrical system crap that the former owner of said beast redid with only 2 colors of wire that collectively cause it to burn through batteries and starter solenoids like they're cheap!) Granddad had a 68 Chevy pickup into which he shoehorned a Detroit 4-53 (with an Allison trans of similar vintage and no park gear) in and claimed nearly 100 mph, which I suspect is a little bit of an exaggeration but I do know that the 53s will (usefully) rev to 3k which is a bit higher than other HD engines, even other detroits. Has anyone here done this? I should think, having not really measured it yet, that a 6V-53 might both fit better and be easier to access for service once it was installed. (the back of grandad's valve cover is up against the firewall) There is all kinds of space under the hood; I can basically sit in the engine compartment with the 6.2 since the AC compressor is long gone. I would consider a small Cat, for fuel economy purposes (I don't have to worry about emissions as we've nearly reached the magic 25-year mark) but they don't usually like to rev as high and even if they do once, they don't twice. Any other suggestions I might consider? I haven't worked much on other makes, but I'm not afraid to try. Cheers!