If you do...let me know. A local guy where I live is running that setup in his Pup and i'll try to give you as much info and help as I can. I have a well-built 1.9 out of an Impulse, a 5 speed, and a newer Isuzu rearend out of a mid-eighties Pup in my '78 stepside and it's pretty quick - but I'd be a fool to race him.
His little shortbed Pup is pretty damn impressive - in fact impressive enough that I'm getting ready to make building a wicked 2.3/2.6 hybrid my summer project...lol
I've done everything to mine that can possibly be done to my '78 to make it lighter and faster except that - so if I can help you in any way - just holla.
If you are looking for a decent late model 2.6 and the carb intake/distributor out of an 2.3 - I'd check here:
http://car-part.com Then I'd tear it down to the basic short block, do a complete gasket replacement, add a reground cam from here:
http://www.deltacam.com Then you can get a pacesetter header that you can get on Ebay pretty reasonable, a 50 amp alternator that you can go to the parts store and get by simply asking for an alternator for a Luv with A/C for the same price as the stock 35 amp one, add a cheap Accel high output coil, and bolt on a used Weber 38/38 that you can pick up on Ebay cheap and rebuild cheaply by getting a rebuild kit on ebay too.
There is an adapter available that allows you to bolt up the stock Luv air cleaner to a Weber carb - so it shouldn't be too hard to BS your way through a smog inspection. Also,when you convert to the higher output alternator - all you have to do is install a heavier guage wire between the alternator and the battery, and replace the fuseable links where that wire conects at the battery with a couple of 50 amp blade fuses and holders that you can buy at your local auto parts store cheap.
And if you want to convert to a 5 speed/rearend combo out of a newer Pup - I can talk you through that easily - and you can do it all in one day if you have the parts and tools handy.
I know..I know...it all sounds complicated - but trust me - it's all real simple basic stuff.
The bottom line is - a Luv with a built 2.6/2.3 hybrid, and the right setup and running gear would be one helluva fun ride. (And if you didn't live so far from me - I'd be more than happy to help you build it...lol)
Good luck....Taz