My .02 worth.... which ain't worth much.
I warn all of my friends about this all the time. Everything you do to the car costs about the same... i.e., a motor rebuild is a motor rebuild... paint is paint... upholstery etc. So I tell them to watch out for a couple things... "rare" means not popular and therefore ='s parts shortage... or high cost parts. So why do some obscure brand/model and just make your life that much harder and more expensive. Unless it's your grandfathers car and has been in the family since 1929 -- move on -- and pick something that will at least return SOME value when you either loose interest - or want something else. Being 50 grand into a car worth 15 grand is just not what you want to do. Being 50 grand in a car that will bring 35/40 is still a loss but not nearly as bad/painful.
Start with the absolute best BODY you can find.... because that's where all the money and time will go up in smoke - trying to buy some clapped out "bargain". Pay up -- WAIT -- BE PATIENT -- don't get emotional or in a hurry.
Be realistic with your skills - your friends skills - your tools - your place to store and build - and with the REAL costs of doing all this... it's double what you thought and takes 3 times as long.
Having said all that..... nothing brings more smiles per mile --- or will gather more new friends. It's a hobby. Treat it as that. Build what YOU can afford -- not what other people expect you to build.
And no t-tops.