Hi John, welcome.
You should go and seek out a BB and TR and experience them for yourself. No point in us trying to tell you what you should buy. I think you should fit in the BB with maybe a little squeeze - I'm 6'1, 180lbs and I fit in without any problems and have some headroom. Of the Pre-1985 Ferraris I think the BB is one of the roomiest.
If you can, try the BB, BBi and TR. There is a big difference in driving experience between the BBi and BB, the latter being much more civilised. Whether you actually want that or not, is a different matter. Don't forget about the 365BB either - it is the rawest of all these cars and for me, that was the reason I bought one. The fact that it is by far the rarest also influenced my decision, but principally I bought it for the noise! Have a read through my article in Ferrari Life Quarterly #10 (I think) where I describe driving all three Boxers, and Boxer's article in FLQ #2 where he describes the differences between the 512BB and 365BB.
My experience with TR's is non-existent but I think it is safe to say that the later the boxer engine, the less maintenance it needs. The 365 and 512 need a lot of TLC and recommended major intervals are 2 years, regardless of mileage. Costs for this are high (sort of Russian roulette with your wallet - if it's $5k you are having a great year - but the biggest part of this is labour and if you do the work yourself you save a lot).
For the TR, I would expect around 20% saving compared to Boxer maintenance. But I don't know if that is accurate or not, not having personal ownership experience with them. One thing to remember: build quality for Ferraris took a real nose dive at the end of the 80ies so there are some rough Testa's out there even if they are low mileage.
I guess that is true, though, for all these cars (Boxers and TRs) - they are now affordable for a lot of people that underestimate the cost of running one of these cars, causing a lot of them to deteriorate rapidly.
One thing to consider if you want to do your own work like you say: the older the car, the simpler it is.
My advice: when buying, expect to spend another $10k, no matter how good the car is. You can only have a windfall, but it's more likely you need to spend something. Have a PPI done. Don't buy from a private individual without consulting a Ferrari expert. Don't trust the belt service if it is included within the sale price, unless the shop is very reputable.
Finally: buy the best you FIND, not the best you can AFFORD. Unless you like rebuilding a scruffy one - there's fun in that too.
Best of luck,
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