My bad--the reading for the compression test were from 90-105 (90,100,100.105.105.105 )
Ok, that's still reasonably good. The lowest is only about 10% below the average. No doubt you're losing some power, wouldn't want to go racing with that motor, but it should run fine for the street. I've certainly driven much worse.
When starting cold at idle it sits at 50 as the motor runs to temp the oil gauge slides to slightly over zero (why i said 2 LB) revving and it comes up to 40-50 and the idles down to zero plus 1-2
I can't say the oil gauge is accurate ,i do believe it indicates a problem
Well, the old rule of thumb for minimum oil pressure is 10 psi per 1000 rpm. Since you're looking at a 40 year old version of a gauge that wasn't all that accurate new, it could easily be the gauge off by that much. But I'll agree, it could probably use some new bearings, and check the oil pump while you're in there.
The question is what is a acceptable number for a compression test
The absolute numbers are not really important, since they are affected by all sorts of things including compression ratio, temperature, even humidity and altitude. What you want to look at is the variation between the numbers. +/- 10 percent is considered about the limit for a "healthy" engine; but they will usually still run well enough at +/- 20 percent (although idle may be a little rough). When I got my previous TR3A, one cylinder was down around 85 while the other 3 were around 130! I drove it that way for about 6 months, until I had time & money enough to stuff a set of rings in it. (Then another 2 years before I put in the set of liners & pistons that it really needed.)
If the low compression is from leaking valves, then continuing to drive it may do some damage to the leaking valve seat, possibly pushing it from repairable to needing replacement. But even replacing a valve seat is fairly cheap compared to the overall cost of an overhaul. And if it's just rings that are leaking, they aren't likely to do any more damage than you already have.
That said, changing the rings and lapping the valves isn't that hard for a "shade tree" mechanic, nor does it require a lot of special tools. (It does require some, just not a whole lot.) And it can be done with the engine in the car (so you don't need a hoist, place to store it, etc.) If you just want to squeeze a few years use out before doing a proper overhaul, you might consider rings along with bearings. In my case, one of the rings was actually broken in the cylinder with low compression, so new rings helped a lot even though the cylinder wall was in such bad shape. The rings had apparently rusted to the cylinder during storage (before I got it), leaving a row of rust pits around the cylinder. The bore was visibly oversize through the section with the pits, plus some of the pits were still there. I put probably 30,000 miles on it that way (drove it to work almost every day and all over the place on weekends).
PS, never did get around to doing a proper overhaul on that engine. The OD had quit and I bought another TR3 just to get the OD out of it. Its engine ran better, so I swapped the engine along with the OD. Never heard back from the guy who bought the TR3 with my old 3A engine in it, but he seemed anxious to buy even after I explained what had happened, so I guess he was happy.