OK, thanks for the informative responses.
Let's focus on item 3.
The electric fuel pump should be fed directly from the fuse box, thru a fuse of course, and never from the ignition coil.
The coil should never be the source for power for anything, ie. electric choke, fuel pump, horn, whatever.
The power going to the coil is being sapped by the fuel pump.
Rewire the fuel pump properly and lets see how it runs with 12VDC going to the coil.
Item 4, the IH air cleaner should fit the Scout II engine/chassis properly with some room to spare,....unless maybe your body bushings are worn/collapsed. You need an air cleaner with a 5 1/8" diameter base opening.