First off let me thank everyone for their advice!
Especially this time around.
Now I have decided I want to do a frame swap. I will look around for one that works well.
You're not the 1st and won't be the last not to like bad news.
So, some assistance in your search:
Terms RC - Regular Cab, SC - SuperCab, SB -short bed and LB - Long Bed
Frame:
The '98+ frame is modular; it split front and rear just behind the cab. There are 16 rivets holding the 2 pieces together.
Ford made 6 front sections - 3 coil sprung (RCSB, RCLB and SCSB), and 3 torsion bar (RCSB, RCLB and SCSB). The difference between the RCSB and RCSB is the frame rails are 6" longer on the LB frame. The difference between an Edge (2wd with Torsion bars and 4WD), is a bracket to mount the front axle to. The LB front frame can easily be shortened to SB length (few minutes with sawzall, drill) Then you would need 8 - 1/2" bolts and 8 - 7/16" bolts to reconnect a SB rear section. Getting the bracket from a 4wd and welding into Edge frame is next level more involve (no longer strictly bolt up). Extending a SC or SB frame for a LB is more involved - you need to weld on a 6" extension (and some "fish plates" to ensure strength).
and 2 rear sections: LB and SB. The LB being 6" longer behind the rear wheels.
Short answer: Any year from 1998-2011 Ranger 4x4 or Edge RC frame can be used as starting point for 4x4. Technically, you only need the front 1/2. If you get an Edge, you will need front spindles.
Front Axle:
Ideally, you get one with same ratio as the rear, otherwise, you need a matching rear.
'98 - mid '00 have vacuum hubs for which you would either a. have to plumb in all the associated vacuum controls or b. convert to manual locking.
mid' '00 - '11 and Explorer '96-'01 have full time hubs.
Aside: Edge + V-8 Explorer = all parts to make 5.0 Ranger 4x4.
Note: '04+ and Explorer spindles have larger brakes. (12.0" vs 11.26")
Rear Axle:
9 chances out of 10 your will want the lift blocks and u-bolts off a 4x4. You can lower the front to run without, but rarely do people do that.
Transmission/Transfer Case:
I'm a wimp, getting transmission/transfer case out of 4x4 as combination is the easy solution. Ideally you are matching manual with manual or auto with Auto.
You can pull the rear housing/output shaft from an existing 4x4 transmission to mate up with transfer case, but for an automatic I would only do that if I was rebuilding the transmission as you start from the front to get to the output shafts.
Transfer case - >90% of what you find will be electronic shift. A manual shift is sooo much easier. Get the wiring in either case.
Cab:
If you get electronic shift transfer case and want it to shift from dash, you will need to rewire the dash to install the 4x4 GEMS. At this point you basically HAVE 2 HAVE a '99-'00 dash to work from, with same engine, same transmission, same drive, same options - e.g. a/c, power window, etc.
I've probably missed a couple, but those are the highlights.
I've restored 10 damaged '98 -'00 Rangers to working condition (out of 12 + 2 Explorers); 6 are still in extended family hands. Closest to what you are doing that I have done is the Edge to 4x4 + V-8.
I've assisted with SAS of coil Ranger - but that truck wound up lifted 8"+ to get clearance/larger tires, and wasn't exactly as daily driver after - fun truck though.