The formula S came out in 65 with a 235hp 273 4bbl same for 66, 67 came with 273 4bbl or 383, 68 came standard with 340, 383 option, 69 340 standard, 383 option 440 limited option.
The 273 has a tiny cam 235hp cam .415/.425 248/248
I wonder how much power a 273 would make with 340 heads, intake, cam, carb and exhaust
?
Looking at the standard features of the 273 64-67 Ma Mopars best parts went into these babys
Forged cranks went in
64-67 273's
67 318's
68-71 340's
273 pistons lightest small block
64-67 2bbl 530grams
65-67 4bbl 569grams
68-69 547grams
360 584grams
318 592-594grams
340 720grams
Adjustable rockers came on
64-67 273's
70 340 T/A motors
Forged vibration dampers
64-69 273's
67 318's
68-72 340's some 72's were not
Mech Cams
64-67 273's
no 340's
Another thought t/a motors cam
hyd. .430/.444 268/276
same as 70 340 non t/a cam, but not the largest small block cam in 68 340 manual cars had a .444/.453 276/284
Some in theory the 273 and 340 have the same parts rods, crank travel, journal size, dampers, rockers. Adjustable not roller tips but hey you could run a Mech. Cam.....
If 1 had a junk 340 (bad crank or 72 or 73)(72-73 do not have forged cranks, there not junk) a 273 donor engine would supply a lot of good parts..... 273's are cheap