I thought I'd better reply to give an update for people searching in the future.
It's out!
I changed my blowtorch from butane to butane/propane mix for a bit more heat and kept heating the engine casing and hammering the crank.
I also tapped out the M6 holes that were stripped to M8, and then when they stripped I went to M10. At this point I thought I was getting a lot of movement, but it turned out that it had cracked the mag flange.
I kept the bolts in to add a small amount of pull to assist my hammering, but the flange soon fell off.
The heating and hammering continued. After about 4 hours there was a 3mm gap. As I couldn't really see the gap increasing it felt like nothing was happening, but using feeler gauges and my vernier kept reassuring me I was actually making progress. I also scored a line on the mag flange in the gap, so I could see if it had moved.
Day 2 was another 4 hours, but this gave me another 5mm of movement. Day 3 was 10mm and as the contact area was reducing I started making better progress.
Then I got to the stage where the con rod needed holding central so that it didn't catch on the little triangular pieces in the cylinder hole. A sponge tucked in there was employed for this purpose after my other half looked like she had enough of being my con rod holder while I swung a club hammer and blow torch about.
Eventually it gave up it's 60 year hold.
A couple of things to keep in mind if someone else is in the same boat-
If it's really stuck, then the crankshaft will mushroom over, even when using a copper mallet. It's worth putting a bolt in the hole in the end of it and hitting that, otherwise it might not fit through the bearing. Luckily mine just fitted through as it was too mushroomed to get a bolt in by the time I thought of that. It'll also be useful if you're prepared to sacrifice a socket, as your drift won't slip off then.
Find some firm rubber about 10mm thick and cut it so that it fits in the casing. Cut a hole in it for the crank to poke through. This way, if you miss one of the thousand hits you'll be doing with your club hammer, you won't damage your engine casing. Don't forget to take it out every time you blowtorch it.
Take your time. Although progress may be slow, it's better to be slow than get frustrated and damage the engine casing.
I then faced my next challenge. Those 4 screws holding in the bearing cover.
They looked like they were the originals and had no signs of ever having a screwdriver in them. They were centre punched to hold them in place.
I dug out my impact driver and found a good fitting flat headed screwdriver bit. I needed an extension bar to make sure he impact driver was clear of the casing and so it could be held perfectly straight.
I used a pick to make sure the screw heads were completely clear of crud so the bit had the best chance of gripping.
One good tap while twisting and the first screw came out. This was followed by the other 3. It couldn't have been easier!
Maybe all the heat and weeks in diesel had actually done some good.
Now everything is cleaned I can start rebuilding with new bits. What could possibly go wrong with that.
![Rolling Eyes :roll:](./images/smilies/icon_rolleyes.gif)
Thanks to all who contributed with advice above. I couldn't have done it without you.