Bill,
I'm not familiar with the 'Palstar', so can't say how
'suitable' it would be. There are a number of the 'older'
(used/cheap) tuners that should work fine, though. I have
an old Dentron 'MT-3000' that will match almost anything
you can hook to it, for example. Something of that nature
wouldn't be quite the inve$tment of a 'Palstar' (maybe?).
You're right, there used to be many more of the 'bread-
slicer' sized variable capacitors around than now. They
were used for a lot of different applications where high
voltages were present (as in matching 'odd' impedances).
You also have other options, changing feed line lengths
to the loop for various bands. Not exactly the easiest
thing to do, but it certainly will work. Or, experimenting
to find a 'magic' feed line length that is a good compromise
for multiband use. Ask Cecil about that...
'Doc

PS - If you happen to run across a dump truck load of those
old 'bread slicers' I would gladly take them off your
hands...(he said with $$$ dancing in his eyes).