FTB

I just got a beat up FTB off ebay , the only thing thats wrong with it is the frame counter doesnt advance. I think its because there is a small dent close to it stopping it from resetting to S. Is this a nightmare to take off the top and maybe push the dent up. Also can you use newer fd lenses on the ftb, doesnt seem like it wants to go on, dont want to force it

I have used a couple of FTbn's for years, and can confirm that you can use both the old type breech lock FD, and the new lenses, but ensure that you press the little button and unlock it from the " A " position before mounting it on the camera or it can't be fitted
I don't know how to fix your film counter,I would think it would be a simple job for a repairer and not cost very much.

As I recall there is a timing consideration in removing/installing the top cover to the FTb.
The meter coupling is a rack & pinion system that must be set at the proper ISO and shutter speed on reassembly. Unfortunately I don't recollect if it was highest ISO & B or lowest ISO & B.
The top cover is probably causing the counter problem though, another possibility is the counter window being stuck between the counter & cover.