i wouldn't say i ever did a real "build" before i found the internet, but i did have a series of rusted worn out POS cars that i spent a lot of time and a little money on..
my first car was a 78 Cordoba with a green vinyl interior (no rich corynthian leather for me) and a decent running stock 4 barrel 360 under the hood. i upgraded it with chrome valve covers and a Kraco stereo that played tapes backwards if you hit the "reverse" button just right.. that thing went thru used 235/75/15 tires on the right rear for some reason..
then there was the rusted 76 Monte Carlo that i decided to do a Northern rebuild on the perfectly running 350 for some reason... i got the tiniest cam they offered and learned how to tune the stock quadrajet so well that it beat all my friend's cars out on our unofficial 1/4 mile track and still somehow managed to get an honest 30 mpg if i drove it nice.. i don't know why it got that mileage, since that same engine only got 10mpg on a good day in the 1970 Nova and 15mpg in the 79 Malibu that it wound up in later..
i had a 74 Monte Carlo that i put a 454 in just because i had it. it wasn't as fun as i thought it would be, so i sold it for peanuts and got a 67 Impala with a generic 70's 350 and a Saginaw 4 speed that was fun to drive but not exactly reliable and had drum brakes that kept going out of adjustment..
i drove 66 Lincoln 4 door that i picked up for $300 for most of the summer of '94. 11 people fit in that one, with 3 of them riding comfortably in the trunk. it was rusty, so i traded it for a non running 70 Nova with a locked up Buick 455 in it- that was the Nova that i mentioned in the first paragraph..
oh, almost forgot about the nice rust free low mileage 68 Chevelle Nomad wagon... 307/powerglide with no options beyond power steering and power drum brakes... i fit 11 people in that car on a couple of occasions..
i "owned" a 66 Impala SS that was a factory 427 4 speed car with 4.10 posi rear and a mint black bucket seat interior. had it for about a week. everything was there except for the engine, and it was solid. the body was in primer, and i had plans for that car. but i needed money and an actual car i could drive so i traded it for $400 and an 86 Dodge Charger.
the weirdest car i had was a 78(??) Cadillac that had multiport efi on it. that was my first fuel injected car, and i can't remember where i got it, what i traded for it, or who i sold/traded it to..