Can I install the bell ,the 4 shims, and the fastening collar to check for proper adjustment with the tranny just lying on the floor and not mounted on the frame?
Yes - follow the instructions in the Shop Manual for determining how many shims/gaskets are needed.

http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0711.html

Also the inside of the bell is scarred up somewhat, probably too bad to smooth with emery paper. Will it be ok to use it anyway or should I try to find a ggod one?
Maybe - Maybe not. It depends on how badly it is scarred and if the scars are near the cork seal on the retainer.

If I need a better one where could I find one ?
Jim Carter used to sell a reproduction bell/cover. He also sells used parts. You might want to call them. Or, post an ad in the Swap Meet.


Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.