Nice Tony,
Conversion components here in NZ make different shifters for the supra gear box. They say they have six positions for the lever. Measuring from the front of the gear box, where the bell housing bolts on, they go from 365mm, 390mm, 455mm, 515mm, 530mm, and 580mm.
This might solve your need to remove metal and also give you a better gear change. The po of my z bent the gear lever all over the place to get it in a place where you could raech it, 350chev and supra gear box. I will be geting one when the time comes.
www.conversioncomp.co.nz
Cheers
Douglas