Have any body done the conversion to EFI with the same 4.2 motor???
search for 2F-E. it involves the ecu, engine harness, distributor, head,intake/exhaust assembly and injector rail from an fj62 3F-E motor with EFI. the head gets swapped and the fuel delivery, intake, exhaust assemblies gets installed, the dizzy gets swapped and the whole thing gets wired to the fj62 ECU. the fuel pump on the block gets removed and blanked and some guys use an inline electric pump, other guys swap tanks to keep the factory in tank pump. there's a bit more to it than that, but that's the basic procedure.
Some guys have done TBIs adapted to their 2F intake and then run an aftermarket ECU.
I have been looking hard at going to a dedicated propane with turbo...