" . . . the block is a '54, head is '52 . . . "

A 1952 head on a 1954 block is an interesting combination.

1952 - 15 head bolts - 2 rocker arm bolts through the top of the valve cover
1954 - 18 head bolts - usually has a 4 screws around the base of the valve cover

The 1954 engine is a high pressure engine (0-45 psi), 1953 and earlier engines are low pressure engines (0-30 psi).

Post the codes that you find in these locations - on pre-1954 216/235
Post the codes that you find i these locations - on 1954 or later 235/261

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.