Hi,
I have a 1970 roadster with an L46 350/350 and an M20 wide ratio 4sp manual transmission. The clutch is almost new and the flywheel has been resurfaced. When engaging in first gear the front end frequently shakes and vibrates. If I very gently ease off of the clutch I can avoid this, but it definitely has a problem. The car shifts cleanly up and down and there are no other problems apparent. Any ideas?

Sounds like clutch chatter and it should have been fixed with the work you have already accomplished. Did the symptoms go away with the new clutch and resurfacing the flywheel and then come back to haunt you?

I agree with Glenn. Sounds like clutch chatter. Check your transmission to bellhousing bolts. If those loosen up, then your car will shake when you go to take off. I had an old Chevy tow truck that did that every so often. Loctite solved that problem for me.
And putting in an "almost new" clutch in with a new or resurfaced flywheel can cause a chattering clutch. Due to the fact that the clutch already has a slight wear pattern and the flywheel has no wear pattern wore into it yet. That why it's better to put everything in new together, so that they can "mesh" together forming their own wear pattern. Let us know what you find out.
Good Luck Sarge

In addition to the other suggestions, also check for loose or broken motor or trans mounts.

Thanks for the feedback. I checked these things out and I do have a bad motor mount. I have a new one on order and hopefully this will do the trick.
Cheers - Tony

Good catch...!!! I wouldn't have thought of the motor mount. Something to save away in the ol' noodle for when "The Toy" demonstrates those symptoms.