Tonearm for Technics SP-15

I have a Technics SP-15 turntable with a Grace 707 arm and a Grace F9E cartridge with a Soundsmith new stylus.  This combination sounds great but is limiting.  The 707  tonearm has a fixed headshell and it does not allow me to easily swap other MM  high compliance catridges or match compliance requirments MC cartridges.  Suggestions welcome from those more expert than I.  


Yes, I have an SME 3009, sliding plate, but no VTA on the FLY.

I found a GST-1 just listed in New Zealand, sliding plate with VTA on the Fly, and magnetic anti-skate

I'm pretty sure it will fit his SP15 Plinth, would need to confirm the rear length and height.

seems to be a good price


just for the record, both technics EPA-100 and EPA-250 are 235mm + 15mm overhang = 250mm effective length, the maximum length for the SP15 OEM bases.

that's 9-7/8" effective length.

I want to thank all audiogon members who posted advice and recommendations.  I learned a lot and finally placed an order on a technics a fully loaded lightly EPA-a250 on a B500 base kit.  Separately, I found a base panel for the B500 that was made for my technics SH-15b3 base cabinet/plinth.  All should arrive in the next week or two and once I set up I will report again.  Thanks again!!

This afternoon my dear friend Elliott helped me set up the base and tonearm along with my Grace F9e cartridge.  We got a little frustrated when some of the adjustments to the arm lift and anti-skate seemed  frozen. Some drops of sewing machine oil and working the mechanisms loosed up and the issues went away..  For a while we were considering sending the package back as faulty.  A little patients payed off and the resulting sounds were fabulous.  Thanks again fellow audiophiles for all your help and recommendations.