I've got two thou's with A14's - here's a list of woes I've come accross.
Gearbox - it's the biggest one as beattie has mentioned the tunnel up near the firewall needs some gentle massaging to allow the 1200 clutch cable to oppereate freely.
You can get away with a A10 box but i found even moderate driving caused slipage in the clutch after a while it's just so small!. Using a 1200 box negates the need to machine imput shaft as well!
The air filter will foul, I cut down the lip of the oringinal pan on one and used a thinner filter and it cleared - just! or as mentioned go aftermarket - or go sidedraft........you know you want to!

No bonnet clearance issues here!!
Engine mounts - the thou has funny angled mounts which are bloody hard to replace - if you can modify the bracket from the engine to accept 1200 mounts your winning before you know it!
I used a A12 dizzy on the A14 all wiring was the same as far as I can remeber.
Good luck!