I would definately replace the fuel filter, it's cheap and easy to do ,
and who konws, it may just be your problem.

I bought my '81 from a guy who was totally frustrated with problems
similar to yours.  I tried to drive it about ten miles and it kept
cutting out every mile or two. Ended up towing it home.

When I took out the fuel filter, it was literally like a pepper shaker,
with little bits of rust and dirt coming out when I'd shake it, so I
changed it for a cheapy translucent one. I then drove the vehicle 200
miles w/o a problem.  Changed the filter (pepper shaker) again after
that, and again a month later.  Turns out that the filler neck was the
source of the pepper, cleaned it this past summer, no troubles since.

Cheers, and good luck,

Bob Norman
'81 Westy
Gander, Newfoundland
Canada