[oletrucks] Accel distributor: vacuum source?

[Josh Keady <keady84@msn.com>]

This is kinda' off topic, but the parts can apply to older trucks too, so
here goes:

My dad and I just put a new Edelbrock 600 carb and Accel HEI distributor on
his '70 3/4 ton's 350.  The little sheet of information that came with the
distributor didn't really specify whether or it uses manifold or timed
vacuum.  Anyone know for sure?  (Just a generic Accel HEI distributor,
factory curved for a stock motor.) 
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959