Hi,
Has anybody used this kit from Retroford?.

Retroford Spacer

I use the 30mm one from Caterham, more expensive but does not require the input shaft cutting. The Retro Ford one looks quite thin and is simply a flat piece of metal, the Caterham on is cast and machined to include the register that the bellhousing locates on.

Also note that some 2.8 gearboxes have the heavy duty lay shaft assembly that has an external bearing spigot at the front of the gearbox, my current one does, an earlier one I used did not. The Caterham spacer is cast to clear this spigot, a flat plate will simply not fit. When I used the Caterham spacer with the earlier gearbox I tapped a bolt into the cut out to prevent the layshaft moving forward, simply removed bolt when I used the later gearbox.

Another vote for the Caterham option here. It just works.

Burton power do them, phone them up and they'll post for the cost of stamps etc, not the amount the website quotes. At least they did for me when I bought some years ago