Hey Spud, I've got a 71 GT bonnet currently in spray putty that I hope to finish soon, once I learn to spraypaint.
It has the original XY twist locks same as yours (I've just bought a new kit from rarespares to freshen it up), and I have the steel mount brackets also.
Being a non GT car though, I'm expecting some head scratching figuring out the correct locations to drill the mounting holes for the lock brackets, short of taking the engine out or limboing in there. Any suggestions or know if theres some location dimensions somewhere online?
cheers
Deano