I think the guy’s just fulla crap. I don’t know about the manual transmission but the only way I know of to get a mega 8’ bed anything is go to a limo shop or whoever just specializes in these conversions alone unless the frame is long enough to do all that on the 4500/5500 without cutting the frames, extending them and welding them back together.
It’s just like when I was shopping for my new halfton several years ago- I really wanted the sport hood; the one that has the faux hood scoops on it but if you selected the chrome bumper/grille group, you couldn’t get it. It had to be the sport model or any of the other trim packages that had the painted mirrors, bumpers and grille. I still could’ve gotten it but it would’ve had to come without it and then I’d have to pay them extra to buy a new hood and pay them to paint it and put it on so, I could see the manual trans and a long bed being installed later but I don’t see him buying a full, complete cab.
Oh, and on a side note, I did see years ago where I used to live where a guy had a 2nd Gen Dodge Ram 3500 that actually had a full, four-door cab on it. I didn’t know the guy personally to ask where that came from but I saw it several times. Mexico, maybe? I do know there was a two-door Ramcharger based on the 2nd Gen Dodge Rams but it was only available in Mexico. And speaking of which, during my several trips down to Laredo Texas back when I ran over the road when I had just started my trucking career, I did see either some 2nd Gen or 3rd Gen 4500 and 5500’s when as far as know, Dodge/Ram didn’t start selling those in the states until the 4th Gens came out, correct?