So, did it blow up the first time you did it?
My first time with a TR3 motor was when I was 19. No clue what I was doing, not so much as a Haynes manual to help guide me (let alone the Internet). On top of that, the motor wasn't just worn out, it was blown up. Exhaust valve head broke away from the stem and pounded it's way through the piston and liner. The rod wound up bent by about 30 degrees, a big 'C' shape. The biggest piece of liner I found wasn't much bigger than a half dollar.
No space in the garage, and no time to "do it right", so I parked the car in the side yard, put it up on jack stands, and set about making it run again with the motor still in the car. Used head & rod from another TR3A (Dad found some abandoned projects in a barn), plus gaskets, bearings, liners and pistons from Warshawski's. Fortunately it hadn't run long enough to spread swarf throughout the oil system, so the crank journals were still OK. I was convinced at the time that the blowup was from running with a 4.10 axle and no OD, so I also swapped the axle out. In retrospect, I suspect the carbs were the real problem, and for reasons I don't recall, I swapped them out too.
This was winter in Rensselaer IN, and there was snow on the ground. So I draped a tarp over the top, and stuck an electric heater underneath.
Believe it or not, I got it running and it turned out great. I went back to school and Dad went back to driving the TR to his job (150 miles each way). I don't suppose it has covered more than 50,000 miles since then, but it was still running just a few years ago when Dad lost a wheel and tore the car up even worse than I left it.