On 3/1/2019, Daniel Francis Casey [on the MGA Twin Cam Enthusiasts Group] wrote:
"At the bottom of the Timing Chain Cover you will find 2 bolts that go through the Engine Plate and have nuts on the back. Extract these and make up a curved sturdy bracket to accept the 2 bolts in their correct location. Weld a threaded bolt onto to same so that it comes back a little past the crank pulley and thread a nut onto same. Then weld a small pointer onto another nut and thread that on so as it runs close to the edge of the pulley which now has BTC marked on same.

With the use of a dial gauge, a 360 degree marker or what ever method you choose, mark BTC (180 degrees from TDC) on the bottom of the pulley. Do this before you weld the bolt onto the bracket as you do a dummy fit and ascertain the correct location for this bolt.

Paint the marker on the outside nut white and after confirming its correct location with a programmable timing light etc, lock it in place with the other nut on this bolt. You will need to remove this nut with the welded pointer if and when it is necessary to remove/install the fan belt.

This crude method has worked well for me over the past 30 odd years and I do not mind laying on my back under a Twin Cam.

Cheers,
Dan from sunny Queensland in Australia