cheers all for the replies.
It looks like (as I suspected), I really only have three options.
1) Use the autopal ones I bought, and modify my headlight bowls to suit the parking lamp,
2) Keep an eye out on ebay for some either NOS or second hand 60/55 sealed beams with the aperture window.
3) Keep an eye out for someone wrecking a mk2 rs2000 that hopefully has what im looking for.
Unfortunately given that the latter two options rely on time and luck, I think im going to have to modify the headlight bowls so I at least have something in there.........
Anyone have any sealed beam 60/55w 5 3/4" lights with the aperture window??? :)
Dave