Crew cab frame for reg cab

My 01 reg cab frame was fixed by the previous owner. They cut about a foot long section out of the middle that includes the middle crossmember. They didn’t do it right and it has a slight dog walk. My frame is also rusting out along the leaf spring bracket. I’m wanting to kill two birds with one stone and I’m asking what frames are compatible that I can cut out and replace with. I have a shop with everything I’d need. I have a crew cab that’s been wrecked close but I notice the wheel base and how far front the rear wheel is to the cab. Do I need to be looking for an extended cab or another reg cab to fix mine

 

You definitely want to just find a regular cab frame. I went the same route cutting down a regular cab frame the 1st one I did a frame swap. I got the same result it sagged in the driver's side. Drove me nuts so I hunted down a regular cab frame. Only problem I had was it was from an automatic and my truck is manual. The trans crossmember is 3 inches further back. Here is the link to my build, you can see how I did it. (I didn't have a shop or all the "correct tool's" but made it work)
https://www.tacomaworld.com/threads/the-green-truck-5lug-to-6lug-conversion.660999/

 

Regular cab frame is shorter. Double cab and extra cab frames are same basic length, but mounting points are different for bed and cab in the middle section.

 

Another reg cab frame. All other frames are longer.

I mean, getting a rust-free xtracab frame is going to be better than a rusty reg cab frame and trying to repair the rust, but you're going to need to do a bunch of and

 

You have all the goodies and the skills to use them if the Double Cab can be had cheap and is in better shape then yours go for it.

You will have to move some mounting points nothing a skilled fabricator should be troubled with.

 

Or build one helluva flat bed!