I don't know your skill set or what tools you have or have access to but here's one I made for my 52 Willys pickup. It's made out of aluminium, bent on a break, bolted together at the seams (I've welded most but prefer to bolt them now with lock nuts). I used a plasma cutter to cut the holes out. I've made quite a few different shrouds over the years. That shroud obviously uses electric fans. Using a mechanical fan I would have made the hole about 3/4 of an inch bigger than the fan all the way around and bent a piece to give it a lip but if I wanted to keep it simpler I would just make the shroud thicker so the fan would be about half way in and out of the shroud. That is unless there was a big distance it needed to go back then I would make a tunnel or find a 55 gallon drum and cut a ribbed section out and bolt it to said shroud if it were close to the size I needed. Making a shroud for a mechanical fan isn't a very detailed process, the point of the shroud is to be able to allow your fan to let your radiator operate at the best it can by cooling all the edges and corners with maximum air flow.
