OK, here we go yet again...
Clevelands...
A 351C-2V (70-74 engine code 'H') has flat top cast pistons, open chamber (low compression) heads with small ports and small valves. All 'H' code Clevelands have two bolt main caps.
A 351C-4V (70-early 71 engine code 'M') as flat top cast pistons, closed chamber (high compression) heads with big ports and big valves. All 'M' code Clevelands have two bolt main caps.
A 351C-4V (late 71-74 engine code 'Q') has dished cast pistons, open chamber (low compression) heads with large ports. 71-72 heads have large valves, 73-74 have small valves. All 'Q' code Clevelands have four bolt main caps.
Then we have the 71 Boss 351 and 72 351HO, but these were not installed in Cougars, they were Mustang-only items. A Boss had a mechanical lifter camshaft, forged 'pop-up' or domed pistons, high compression heads with large ports and an adjustable valvetrain. The HO had flat top forged pistons, a mechanical lifter camshaft, Low compression heads and an adjustable valvtrain. Boss and HO blocks have four bolt main caps.
OK, Camshafts...
Hydraulic camshafts
351C-2V 'H' All .407/.407
351C-4V 'M' 70-71 .427/.427
351C-4V 'Q' 72-74 .480/.490
Mechanical lift camshafts
351C Boss 'R' 71 .477/.477
351C HO 'R' 72 .491/.491
Unfortunately, my book doesn't go in to the camshaft timing or duration figures. I do know, however, that the 'Q' code camshaft was ground 4 degrees retarded to help with emissions. If you advance it back to where it should be, you get a real screaming motor! (on 429-460s they retarded the camshaft with a different timing chain set. Put the early timing set on and it will really wake up those beasts!)