Thanks for all the info.
Just replaced the studs with 2" caps with lock washers.
Got a 160 T'stat just up the road at Flying Circus British
Cars here in Durham. (They do have a set of all hoses
should I need to go this way again.
OBTW - they have a gorgeous red frog-eye out front,
and a lovely white '72 RWA in the back yard for repairs.
The body is slick soI asked whether the owner would notice
if I swapped bodies and kept my engine-tranny. No dice!
I'll pick up fresh coolant romorrow and give 'er a go.