I have an 89 Econoline with a 300/6 that only gets 15mpg. I'd like to improve upon that figure. I've read that there are plenty of mods that can be done to the carb versions of this engine to get into the 20+ range. In fact, the older I6s I've had got around 22 mpg without any mods. So, I am thinking that maybe an EFI to carb conversion is the way to go. I do not know if this is even possible. If so, I have created a list of what I think I would need. Any help would be appreciated.

Different intake and exhaust manifold
Carb with breather
Old style distributor
Ignition contol box
Ignition coil
Various connectors

The van needs new exhaust anyway, so I've even thought about eliminating the CAT. I figure I can get a lot of this stuff from a junkyard. Well, except for the carb. I just assume get a new one. What say ye?