[Roadsters] Transmission oil options for U20

[D Riedel]

I read through last August's threads on GL-4 vs GL-5 oil for roadster
transmissions.  Unfortunately, I'm finding GL-4 pretty hard to find.
I did run across some but it was 'apparently' spec'd for GL-4 OR GL-5
and it was $38/quart (yikes!).  I can have some Pennzoil 75W90 (?)
GL-4 ordered in.  It's more like $15/quart... still nasty expensive,
but much better.

What do most people use?
Is synthetic ok for an old tranny (not recently rebuilt)?
If so, which one?

-- 
Dave Riedel
'69 2000
Victoria, BC