Yup, I know of the Aussie sixes. There's an X-Flow powered 66 Mustang in Florida, and I'm working on importing an XD or XE Ute with a 250 X-Flow to here(Canada) to start with, and, I'm planning on eventually getting a TickFord for it. I almost got an X-Flow to put in my F100, it would have been a bolt in using the Aussie frame pads, engine mounts, and bellhousing, but I didn't have the money.
The 300(Same one that you guys had) was last used in trucks in 97(96 in F150's,) but, it's still avalable as an industral engine. It went to MPFI in the trucks in 1987, but, the industrial version is the same as it was when it came out in 1965 except for an electronic ignition system. There are lots of aftermarket parts for the 300, cams, roller rockers, 4bbl Carby intakes, extractors, you name it, the EFI donk is a bit limited due to the S/D EEC-IV up to 96, and the 96's OBD-II MAF system. Mine is eventually getting an intercooled Twin Turbo setup with a custom EFI system.
If you want to, check out
http://pub41.ezboard.com/bfordsixcylinderperformanceforum
It's where Us Ford I-6 nuts hang out....
Evan