Welcome to the forum
The 292 motor mounts are offset, whereas the 230/250 have the mounts straight across. If you don't already have an auto trans, a 700R4 would be a good choice. Although getting the TV cable setup correctly could be a challenge. I do know that this wouldn't be the first 700R4 behind a I6, so someone will surely have answers on setting up the TV cable.
As for EFI on the 292, you would have to go with an aftermarket throttle body injection, such as the Holley.
If you had cooling issues with a V8 before, you likely had an improper setup cooling system, or a plugged radiator. These early vans came from the factory with small blocks, and didn't overheat.