Yeah, LH & RH in car terms is always confusing, but to my knowledge it is always taken from the driver's viewpoint.

When you are sitting in the driver's seat, everything on the right is the the RH side & everything on the left is LH side. It's when people look from the front of the car e.g. standing at the grille & looking at the under bonnet is when things get tricky. From that aspect, the RH side of the engine bay is the LH side of the car.

On the topic of Powerglide gearing, AFAIK all Holden 6 Powerglides & HT 253/308 V8 Powerglides have a 1.82 1st gear, while all the SBC variety have a 1.76 1st. What would most likely be different between the various Holden versions would be the valve body calibration. I'm not sure that the 253 Powerglide & 308 Powerglide are different, but if they were, that difference would be in the valve body. This would mean if you fitted a 308 Powerglide behind a 253 (or vice versa) they would drive differently & not necessarily for the better. The mid throttle kick-down which is critical with a Powerglide, could be affected.

Dr Terry

If you csn find a good auto shop not out to rip you off get it serviced out of the car. Costs about $100. They will adjust 1st gear band and also inspect it for you. I use Barry Stace in Newcastle.
The other thing you can do is get a recoed converter from Dominator with a bit more stall in it if you are going to run a 2.78 or 3.08 rear axle. I did this for my HJ Prem TH400 with 2.78. The converter was about $200 with a stall of about 2100 rather than standard 1700 or so.

See if Dave Smith has fluid lines for you too as well as column mech. He'll advise you on the column too, throttle linkages, engine harness etc. He may even be able to help you put with a V8 banjo centre.