i have been in the same situation for the last few weeks. i am ready to send the car to paint and concentrate on the engine. it has not run for about 7 years, but it was a pretty strong 1835cc when it did run. i know i can get it back up and running and do some minor upgrades (like weber 40IDFs, maybe 911 cooling for looks only not sure if it is a good move considering all issues though) a lot cheaper than i can go TIV. BUT a TIV is still very tempting. i think budget will take me the way of everyone's suggestions here.
one additional thought is i may step up the trans for taller 3rd and 4th gears for cruising purposes (i think i already have the horses for it) in prep for TIV later. have some homework to do there though. can get into that for $750 + install.
check out
www.aircooledtechnology.com jake knows his stuff and has some pretty good info (albeit slightly biased, but who isn't) for what you are looking for. he does many TIV's, TI's and 2 trans.
sorry for the length of the post.