Snowy

My 1800 carlton has exactly the same gearbox and selector as the 1800 manta. Not sure if the CIH engine cars were different.

That is definitely B series

I have a spare pair of shafts you can have for the price of postage.

Be careful you're not chasing something that isn't there. I had a 1900 a series at the same time as a GTE. Whenever we took them out at the same time, to cars shows etc, the A series would always outpace the GTE until at least 60mph. I always thought it was because the A series was lighter, but when I converted my first mk1 cavalier to GTE spec I left the four speed gearbox in to start. With a standard GTE engine and four speed box it also outpaced the GTE until at least 60mph. The realisation when I did fit thr five speed that acceleration through the gears just wasnt as quick as the four speed was. So if you can try and drive a couple of other standard GTEs to see what they are like.

Can you define lacking in power, compared to what? The GTE was quick for it's day, but not compared to most modern cars.

Yes they are, from Vauxhall.

You need spline bits, at least that's what I think they are called.

If you cut the doors off you probably won't need the tool. You'll be able to get a standard punch in. It's only thr curvature of the door that stops you using a punch normally.

You want something like this.. https://www.ebay.co.uk/itm/Laser-Tools-2133-Door-Hinge-Pin-Extractor-Kit-4pc-/271233691314?_trksid=p2349526.m4383.l4275.c10 Loads of different makes and types. I'm not recommending this one, it was just the first one that came up. The hinges are easy to take out if you take your time. For the bottom hinge put the tool in place and rest the bar on an axle stand halfway down. Now you can hit the end with a lump hammer. For the top one do the same again but this time rest the end of the bar on a stand. Hit it closer to the pin this time with a lump hammer. Just be sure to use the right diameter pin.