It is fairly safe to say that all 1954 235/261 truck engines used 5 qts of oil as long as they have the original/stock oil pan and no oil filter.

http://chevy.oldcarmanualproject.com/chevyowner/54tom90.htm

Yes, if you have a 1-qt oil filter, you'd need 6 qts. A 2-qt oil filter was also available on all sizes of 1954 trucks/engines.

Yes, if you have a later oil pan, you could have a different capacity.

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.