Anyone know if an SI block with accept a BW66? Also, will it accept a SII intake manifold with dual Strombergs?

 

I have a spare BW66 if you want to try it.

 

I see no reason why not.

I fitted a '66 into my 3.4 S Type way back before Forums, computers, etc, no issues at all. It had a DG trans, so messing with dipstick, and kickdown cable was just part of the fun, BUT, attaching to the engine, straight in.

I used the S3 flexplate and starter motor at the same time.

The cyl head will accept the SU set up. Some linkage fiddly may be needed depending on what came off it. Once again, not rocket science.

 

The 66 used a cable for shift points, whereas the S1 used Vac and switch. You would have to make sure the cable will work, as its operation is critical.
The S2 intake, if the car had a 65, would have the cable pull where the throttle bolts to the back of the head. You could use that.

The S1 will have the heavy flywheel, and the 66 has a flex plate. I believe either will work. Check for damaged teeth.

For the intakes, compare every hose and connection. There were many types of thermo housings and water pump hose configurations. You might have to swap the S1 bits onto the S2.

Good luck,
Rob