4 studs came out with some effort. One has sheared in the head.

Some comfort that it's one of the central ones that had to come out - I'd be kicking myself if it was one of the outer ones.

I reckon there's sufficient room to attempt a drill out and possible clean up or helicoil in situ. If it's proving difficult, I'll whip the head off.

1972 4/4 4 seater, 1981 MGB GT
1984 Harley Davidson Electra Glide, 1990 Kawasaki ZX10