Having just been through this I thought I'd add some info to the site. For those who don't know, the sandwich plate is the thick sheet of metal between the block and gearbox, into which the starter motor bolts.
These are NOT interchangeable with SOHC items, not even when reversed. You cannot modify a SOHC sandwich plate to suit, because even when reversed, even if you drilled the new holes, the big circle for the starter motor is in the wrong place, and therefore it will not line up with the starer motor recess in the gearbox bellhousing. As far as I can see you won't be able to get past this without major modification and probably welding, and it'd probably be easier to have a suitable sandwich plate fabricated.
The inspection plate, which bolts onto the bottom of the sandwich plate and covers the flywheel and seals off the gearbox (legally required, it would also be potentially unsafe to leave this off) is different, however the SOHC inspection plate may be used. The lower bolts just go into the gearbox, and line up as far as I can tell thus far. The upper bolt holes don't line up, but this is of little importance. The sandwich plate stops the inspection plate from bending or wobbling towards the flywheel, which is the only concern, and if it rattles at all, I'm sure gasket goo could be applied, or a small screw/bolt hole made to stop this.
If anyone has further problems with this, doesn't understand or requires more info, I took a few pics, but I'll only host them if they're required as my internet's a shit. Whilst I doubt anyone else would have a motor so incomplete as to go through all this shit like I had to, I thought I'd be nice and post my experiences and info up anyway
Eli
P.S. You were totally right Poida, thanks for the advice! I thought I'd check but as it turns out there was no point. Oh well!
