You two got in before me so I'll try again.....
Good call Duncan, I was doing mine today using 'Mappgas' (Propylene),I think it' a blend of something like benzene or acetylene and propane?? but gets pretty hot, and the gasket being an odd shape, I found it hard to get even 'cheery red' all over even tried different ways to hold it, never used a heat gun but I wouldn't be optimistic??
Also on the subject, My mate Kel pointed out that there should be no gasket protruding from the joint into the combustion chamber, reckons it'll ping terribly, consequently I spent a bit of time with the file,to ensure that it cleared the top of bore, and also on the R/R (?)& S/R heads I noticed that there is a bit of a relief in the head for the valves
, so extra whittling.