I've been taking a close at the Edelbrock Pro-Flo 4 EFI, and it seems to be a good choice if you want multi-port injection. It will cost more than the Holley Sniper, but probably not enough to break the bank.
Another challenge you have with EFI is to figure out what to do with your gas tank(s) to keep the system fully supplied with fuel. A low mounted electric pump may work fine, but in-tank pump or an external fuel sump would work better. Some pumps or EFI systems also require a fuel return line, which you might not have on some trucks.
If you install an external sump you can still keep dual tanks and feed the sump from your mechanical pump connected to the tanks. The sump then has the high pressure pump to feed the EFI. Edelbrock, FiTech and others sell the external sump/pump systems.
Bruce