Well, you asked for help and nobody else seems to be jumping in, so.......

You told us what you wanted, but I myself would do it different. I would forget about keeping the stock oil filter appearance. Trying to engineer around that thing would give you two strikes before you even start. Use of the existing space, yes. Keeping it stock, eh.........
First take a measurement of exactly how large of an air cleaner will fit in the existing space that you have. Then with the measurements you got, visit a late model truck or bus salvage yard and look at some of the dry filters that would fit in the space that your truck currently has. To get the new one to fit will require some new brackets, a little engineering with a welder and probably some exhaust pipe bent to route the new air passages. Before you attempt to start on this project, have you priced some of the air filters on these late model trucks? You can buy a lot of non-detergent 10W for what a large air filter costs.
Well, you got my advise. While it may seem that I'm telling you to stay with the air bath, I am not. I'd probably also switch it to a dry filter. (Just my $.02 worth of advice) Good luck.
If you DO the swap and keep it original looking, post some before and after photos.