I haven't read all of the post so if there is repeating sorry.
My first suggestion is do not use the Chebby, yes it is not a Ford but the Chebby is longer than a Ford 5.0L, it is heavier, it is wider and the possibility of getting a radiator to cool it in the small engine compartment is low.
The wider Chebby will create more problems with header than the 5.0L Ford and the longer engine will create a need to have the radiator out the front of the truck or a major firewall mod to pull the engine back.
The easiest V-8 setup for a Ranger is the SB Ford, any of them from the 221 up to the 302 and any strokers in between. The 351 creates more trouble (like the Chebby) than they are worth, especially with the stroker kit out there for the 5.0L/302s.
I did the 5.0L Swap in an '88 Ranger, using an L&L kit, (Headers were really good) all went well but the radiator was another thing, cooling was a major problem even with an aftermarket setup. Part of the reason was the radiator had to be moved under the front support to give the clearance necessary to fit the, short than a Chebby, 5.0L and no mechanical fans; the electric fans raised hell with the radio equipment in the truck. I got a little relief from the heat by jacking the rear of the hood up about 1.5 inches (poor mans cowl induction) dropped the temp about 10 degrees.
My first run to the Vermont Truck Show was in the month of August and the heater was on full to help with the engine heat, talk about hot feet.
My next V-8 conversion is going to be an Long Rod, EFI 230 CI SB Ford based on a de-stroked 5.0L with NV 3550 trans, T/C still pending, and L&L Adapter Kit; time will tell and the result will be interesting.