Stude, NOTHING easily fits in the little Rambler engine compartment except a straight six with an integral intake manifold. A small block or V-6 can be made to fit, but requires a bit of trimming of the inner fender panels, and exhaust is tight. The narrow V-6s are a better fit except for accessories. Get hot-rod (30s style) high/narrow accessory mounts and you're all set.
Ramzoom may have to trim the inner panel on one side for the Q4 to clear the intake. Not much needs to be trimmed, just the "hump" right above the upper control arm mounts. The hump is a leftover from the early 50s -- the unitbody is virtually the same from 50-55 (Nash Rambler) and 58-60. In 61 the outer panels and firewall changed, but the rest is the same as earlier models. This is the only car that ever dropped out of production from more than a year and was revived as a successful product -- with minimal changes.
When Ramzoom gets some engine bay photos you'll see just how tight it is! I hope he posts a photo with the original engine still in (but I think it's out already...), or at least with no engine before hanging the Q4 in and getting photos.