340 with 35 degree at 600 idel and 200psi compression

is your vacuum advance hooked to ported or manifold vacuum? It should be ported vacuum...or better yet, make sure its disconnected when you're setting the timing. Because you could loose tons of advance the second you move the distributor if you're on manifold vacuum. you should be able to keep it revved up a little (1000 or so) and set the timing there to 10-15 degrees BTDC. It should run fine there.

otherwise, your cam timing may be off!