''I just got a windscreen for my gp and its 42 inches across.so its not a gp one was thinking about getting it cut to size and re welded.any thoughts about that thanks.''

That'd be a tricky weld on commercial ally with that profile.

Don't alter the screen until you measure your bonnet as GP used many different sets of moulds for the Mk 1 Beach Buggy and sizes can vary. Plus not all GPs are genuine, there were several direct copies.