My 340 build

you do NOT want a thumper in that high compression motor
Whiplish instructions get it right

just look at the lca at that duration realle early intake close
fkn comp
get the lunati call around
jegs or lunati for a list of their distributors

a wider lca will cut the cylinder pressure down also
(retards intake close)
that 268 -you could stick it in straight up (4 degrees retarded from what they recommend)
still I do not like that cam
a stock cam would also work till you get the right cam
you might pm dart19666 and see if he has something on the shelf- but not their short catalog cams- they are mass produced- no better than the comp- larger ones are good
a 281 would work but not in catalog