Slant 6 198 Connecting rods

You could measure the stroke of the dead block to determine displacement.

Engine Bore Stroke Disp Notes
170 3.40625 3.125 170.9 1960-1969
198 3.40625 3.64 199.0 1970-1974
225 3.40625 4.125 225.5 1960-1983
(225: truck/marine to 1991)

Specs cut and pasted from a page at Allpar.com
Thanks Allpar for being convenient.