Not a clue! You might have to take it to your nearest weigh station to find out for sure.
You can thumb through a few good books at the local libarary or bookstore to find out what the GVW was when the car was originally sold and you could get into the ballpark, but you'd still be off for your differences in engine/tranny/frame changes.
If I knew how much my coupe weighed I'd tell you, but I don't so I wont!
I just thought of something? Do you guys have weigh stations in Great Britain like we have on the U.S. mainland (where tractor/trailers are required to pull in and weigh themselves on occasion to meet road weight requirements)?
If it's not running, go weigh a trailer, put the car on it and weigh them together, then subtact to find the difference.
My coupe is VERY light... and yours, depending on if you run fenderless or with aluminum heads and such could be really light too.
my 32 sedan, steel body, fibreglass guards, 283, th350, jag rear, cragars weighs 3000lb with a tank of gas. 32 hiboy roadster, fibreglass body, 283, top loader 4 speed + halibrand is 2300lbs. hope this helps a bit.