Finally scared out some time to put the repaired exhaust front pipes back on the. About 4 or 5 hours on my own with maybe an hours waste dealing with "old car" silly stuff. Doesn't seem to matter how carefully you do prep work, anything short of full restoration mode and it finds away to bite you!
Slow, but 71 is not the new 21, and when you re working on your own with the car on drive up ramps there is a lot of slide in and out and walking from side to side time wasted. At least my ramps are rather higher and much stronger than the usual variety.
After fitting the new studs into the manifold I connected the pipe to centre box very loosely with nuts right on the end of the (longer) bolts and cribbed the pipe up step by step using blocks of wood. Making sure to keep the nearside Lambda sensor wires clear of the prop shaft. Very vulnerable they are. Last inch or so lift by hand and one nut on each side to keep it in place whilst I dealt with the gearbox support cross member. Proper clean off and greasing when I took it off to remove the pipe meant it not only went back in OK after I'd removed the pipe it also came out again and went back easily enough with pipe in place. Pipe does restrict access to some of the bolts so usual futzing around sorting socket extensions to get the torque wrench on. Easy if standing under a car right up on a lift. Trickier on your back with about 6" nose to chassis clearance! But we got there.
Finish bolting the pipes went pretty much just like that as did connecting the drivers side Lambda sensor. Considerable frustration, aeration and creative language trying to fit the nearside Lambda plug. Eventually I realised that jacking the nearside front wheel up, so the ramp could be pulled out and an axle stand put under the chassis letting wheel hang free once the jack was pulled out made just enough room to get my hand past the prop shaft and onto the plug so all could be connected. Getting into the right position to do the job with standard elbow articulation was a bit fraught tho'.
Lost best part of two weeks in prep work including finding a repair kit. Which latter was much harder than I expected. Mrs Google wasn't co=operating.
Eventually discovered AutoDoc could supply a 60 mm repair kit :- Bosal 263-17 : for £25 delivered. Had to wait over a week which gave me time to de-rust and paint to the pipes. Decent quality with repair sections for both pipe and slinger end. Not needing the silencer end part, my back system is stainless, I cut a it down to a stub of pipe and sliced a 1/2" wide strip out lengthways and massaged it to a smaller diameter making a nice tight inner strengthener for a properly permanent job once all welded.
Also needed a new loose flange.
Found a stainless one on E-Bay. £15 from Profusion Exhausts. Chinese laser cut done in rat gnawing mode so a fair bit of cleaning up needed before it was safe to handle. As delivered there was no taper on the inner hole just a sharp square, rough cut, edge. Popped it in the lathe to give it a nice smooth 45° (ish) taper which I figured would work much better at holding things together in a gas tight joint. Bolt slots in the flange were 13 mm, for 12 mm bolts, but the ones on my exhaust loose flange are 9 mm, for 8 mm bolts, So more futzing around making properly deep and strong top hat washers to sleeve the oversize holes down to match the bolts. I've got the workshop facilities to handle that sort of thing. If you only have ordinary garage kit maybe there is a supplier of one that just fits.
PS The Laser Impact Stud remover recommended earlier works great. Wrecks the studs but they came out. Albeit with more rattling from the big Makita battery impact gun than I expected. Heating the flange before trying was probably prudent.
Clive