I'm gonna get slammed for this I know, but the Explorer V-6 would be nice with EFI (or Mercury Mountaineer -- resale value is a little less on them). I'd get one with a 4.0L instead of the 3.8L, but the 3.8L will perform well in a light coupe vs. the heavy Explorer. Bucket seats and disc brake rear axle will be useable, tranny also. Make sure it's a 2WD, not 4WD! You can use the 4WD, but will have to convert the trans or get a 2WD replacement. I don't recall how the 2WD front axle is made, it might be a twin I beam. If so you could do a "C-boy" on the front of the 34...
If you're looking for a bargain and want a V-8, look for crown Vics and Town Cars with the 4.6L. The rear axle will be to wide, and the seats are wide bench though. Most trucks will be the same. Even the bucket looking bench seats usually have the center arm rest/cushion made onto one of the seats or have all the bottoms on the same rails.
A Fox body Mustang would be a good donor vehicle, but will likely cost more than a Vic. Same with T-bird and Cougar.
A Ford Ranger truck should work well for a four or V-6. The Aerostar van would provide the same (at least V-6, don't know if they came with a four), and rear axle and seats (with modified bases) should be useable. If you can find a T-bird turbo coupe or a Merkur XR4ti turbo (or even the non turbo version) those would be super nice!
The XR4 is rear drive and has an IRS tha can be adapted to the 34 frame. I don't know if the turbo version has a stronger diff than the standard or not. I doubt the diff would stand up to a V-8, but should be okay for up to a 4.0L V-6. I just bought a ti for a project and plan on using the diff, but it's going into a small early 60s Rambler. At least that's the plan for now. Mine has a T-5 trans, don't know what they used for an auto.