Short Commutes, coolant filter

[Eric Walter <ewalter@domain.elided>]

About 2 weeks ago me and my wife moved to a place only about a mile (or
less)from where she works.  Her '73 Scout w/345 doesn't get a chance to
warm up and seems to have fouled the plugs already(one or two not firing
consistently).  I don't think the choke is opening fast enough and I'm
thinking about switching to a manual choke. I'm not sure what plugs are
in it, but am thinking about going a couple numbers hotter. The only
problem with this is that she occasionally has to go to Helena or West
Yellowstone for her job (90 or so miles) and I don't want to get plugs
that will overheat and stop firing.
  On a different problem, some former owner must have put about 10 cans
of stopleak in the radiator. I flushed the cooling system for a very
long time last year to get the heater to work, but soon after the
antifreeze was brown as mud. Later when I had to replace a freeze plug,
I discovered that there was a caked layer an inch deep in the bottom of
the water jacket ( I thought about pulling all the freeze plugs and
running a pressure washer in there).  I want to get a new radiator but
don't want to pollute it with stopleak. There was some discussion about
coolant filters on the digest, did I understand correctly that they use
spin-on filters (like oil filters)? I have a remote (dual)oil filter
setup hanging around (never made it onto the vehicle it was bought for),
would an oil filter work for coolant or do you need a special filter?
Thanks for any suggestions,
Eric