You might have to jamm it all towards the back. I had two of em in a 73 Econoline E300 One Ton Van (Super Van it said on the back door) in the 70s and early 80s, actually had that till some scrapper stole it in early 2Ks, while I was away :/
I think it would be super cool to put a doghouse in there somewhere, that would give the extra room for it. You'd need bucket seats to do it that way. Made it easy to fix or tune sittin right there in the driver seat
Good luck with it man