not sure about coupe but i think youd be able to bash out a little section for the switch to fit in

here's what was needed for the 5 speed conversion (it was a while ago so if i miss anything i'm sorry)

1. tunnel massaging - not much just enough to clear the clutch fork as it's a little higher than the b10 box. it will work tho don't be afraid to give the tunnel a good whack!
also a little indent was needed for the reverse switch

2. original gearbox mounts - i took mine out it made it alot easier to install and remove the 5 speed.

3. Rear gearbox mount - i adapted a sunny gearbox mount and made it wider incorporating plates to have the mount bolt onto the floor pan in the footwells I also put plates on the inside to give it some strength.
If you know anyone that can weld or if you can do a decent job this is easy.

4. clutch cable had to be altered - I used an old cable from a 1200 for a while which was spaced out at the firewall with washers but once i had the lenght right I had a new cable made up.

5. tailshaft - here's where things get a bit hazy cant remeber if i had to have it shortened don't think i did

It took me about a week of after hours tinkering to get it in a driving but well worth it. hope i didn't miss anyhting important

good luck!

Good stuff dude, helpful info
cheers Dean