So, 2 months on and the engine has now been almost fully re-assembled. Had a few issues along the way but none that were insurmountable.
Had the head refurbished by Country Engineering at Oldbury-on-Severn which involved skimming, and cutting the valves & seats although most weren't in that bad a condition. The good news is that it confirmed that it is ready to run on unleaded as I wasn't sure before. One of the valves was badly pitted on the face and I managed to get hold of a used replacement. Valve guides were ok so just fitted new oil seals which cam as part of the head gasket set anyway.
Torqued the head down with no problems and assembled the cam towers ok. Assembling the rockers was a real time consuming process as it wasn't as simple as just installing the arms and then setting the valve clearances. You have to check for lash pad wear and possible offset due to any valve seat cutting. The rub area where the cam lobe hits the rocker arm is quite precise and according to the book, you would have to change the lash pads on the top of the valves if it was outside tolerance. It means you have to install the arm with some dye or marker pen on the rub pad, turn it over, take it back out and check how much of the dye had been removed and if it was equal from each edge, re-install the arm and set the clearance. Given that there are 12 rockers, this took the best part of a day to complete. Luckily all were ok and didn't need new lash pads.
The next problem I had was with the valve timing when I installed the new timing chain. Unfortunately the new Cam sprocket didn't come with all the same timing marks as the old one so lining it all up was a bit of a nightmare. I got piston 1 to TDC and got all the marks etc in what I thought was the the right position by using the old sprocket and then swapping them over making sure I was very careful not to move anything. Went to crank it over and found that I was 180 degrees out on the cam position so the valves would hit the pistons . Having already torqued the head down this was a bit of a problem so I ended up having to remove the rocker arms again and set the cam to the right position. All the clearances had to be re-set so another day gone!
Eventually got all the timing gear and cam parts back together and put the timing chain front cover on. Went to tighten the last bolt on the cover and heard a crack sound. It wasn't completely obvious at first but closer examination showed that I had cracked the cover just to the side of the water pump. Luckily it wasnt near any water or oil channels and it was only a small crack so rather than take off the cover again which would need a new gasket and a new cover which isn't easy to get hold of, I ran some solder into the crack as a sort of weld/seal and then covered it with some gasket sealant. I know it's a bodge but hopefully it won't get any worse or leak when I get the engine running. If it does, then I will have to use the one off the other engine when I swap them.
Got hold of all new manifold studs, nuts and bolts and refurbished the set of round top SU carbs I managed to get hold of a few months back. All manifolds bolted together without a hitch although getting to a couple of the nuts and bolts under the manifold wasn't easy.
Cleaned up the fan and crank pulleys with a lot of elbow grease and a wire wheel on a drill running at slow speed. Got hold of a new inlet pipe, heater pipe elbow and Thermostat housing and bolted those on using some new bolts. It all looks nice and shiny. Just the Alternator, starter motor, rocker cover and oil pressure sender to be fitted when I transplant the motor as they need to come off the other engine. New clutch also ready to go on when I take the block off the engine stand.
Will get some pics of the finished engine downloaded when I get the time and weather to be able to wheel it out the garage. All in, I reckon this has probably cost in the region of £900 not including the initial cost of the engine and cost of the carbs. Would have been a whole lot more if I had had to change piston rings, bearing shells, cam etc and machine the bores so I (and my wallet) are grateful for that.
It has been good experience and quite enjoyable given that I am not that mechanically minded. Wouldn't have thought that given the mess it was in when I picked it up, it would turn out so good but the best is yet to come if and when it fires up in the car and I feel the increased power when I drive it. That will probably be in the Spring now unless I find somewhere indoors where I can swap the engine over a few days. Trouble is, I am itching to do it and find out if all this has been worthwhile.