Oil Viscosity,Filter, and Pressure

OK,New to the group here fellas,,..so be nice to me!
Just finished off my 57 Chevy Wagon with a new paint and interiour.It has a 350 out of a 1975 c-10 truck and freshly rebuilt.About 3000 miles on it.i bought it that way from the first owner.Just a simple question on oil viscosity and what filter.
i can't seem to find out anywhere to give me the specs on what is recomended oil viscosity.Also,the oil pressure i have read should anywhere from 20-40 normaly,right? i bought a Hastings Oil filter and back 25 yrs ago they used to use a cotton fiber media.not so anymore?Are they still good,or better? I hear Wix is a favorite.
As far as my driving habits for it...it will be as many Classics,just a Saturday night Cruiser or Sunday drive.And i live in Texas ,so the winters are mild and the summers,well hot as hell. Also it is kind of low geared in the rear,but not sure what it is.So,hiway,it revs pretty high.Hope this is helpful in determining the proper oil visc.
Thanks for any replies,
Lerch

I run Mobil 1 Synthetic 20W50 in all of my motors. I use a 10W30 for the intial run in on the engine, then change the oil to another load of 10W30 for the first 2500 miles then switch the engine over to the Mobil Snthetic. I use the Napa Gold filters (made by Wix) and have never had any problems with them.

By the way, that is a very nice looking '57 you have there !!! Congrats on a job well done !!!!!

Personally, I won't use multi-viscosity oils in warm weather. The friction-modifiers in them just displace some of the oil, and do no good unless its cold out. Even in winter, the more "spread", like 10-40 compared to 10-30, the more goop there is in it.