Decided to fix a small coolant leak on the SD1 over the weekend. There's a heater pipe which runs under the inlet manifold, and elimination suggested this the culprit. Which means a fair amount of dismantling. However, this fitted in with changing the EFI loom for a decently made one incorporating all the changes I've made for the MegaSquirt and EDIS ignition. Everything was ready to fit so a day or so should have been more than enough.
Until I discovered the new inlet manifold gasket was lacking one bolt hole. It's coated in some sealing material, so didn't fancy trying to make a new hole in such thin steel.