Welcome to CHR! Like you have just seen, there are a lot of great knowledgable guys that lke to help. I was going to mention chassis engineering Inc as well. You can buy your engine mount kits, a MII kit, and pretty much what ever else you may need for your chassis from them. They are great people and have great service.

Now, since you seem like you'd like a manual trans, try this option. Find a ZF 5 speed from a mid 80's-97 old body style ford F-150 or F-250. These trucks also have 302's and 351's so you should be able to bolt it to your 302. These have hydraulic operated clutches so fitment may be easier as well. A lot of guys seem to be running 8.8 ford rear ends too lately. Ones from Explorers are pretty popular and have disc brakes. If you have a OD top gear and run a decent height rear tire, you can probably run like a 3:50 rear gear and still keep your goal rpm cruising number. In the next week or so I'll have a parallel leaf spring kit I'll be selling out from under my 40 Ford. It should bolt right on your truck frame as they are pretty dang close to the same aside from some body mount brackets. Good luck on the search for parts, and journey! Sure looks like you are starting with a pretty good truck too!