OK...
A 273 had 1.78" Int and 1.50" Ex valves
A 318 had 1.78" and 1.60".
A 340 (some) had 2.02" Int and 1.60"
A 360 had 1.88" and 1.60"
The 5.2 and 5.9 have 1.92" and 1.625 in closed chamber heads. The ports were raised just a little.
Per (my memory) the Magnum book by Larry Sheppard
The Magnum combustion chamber size is said to be 62 cc.
The inlet port flows about 207 cfm at 0.400 valve lift at 28 inches H20.
The exhaust flows about 171 cfm at 0.400 valve lift at 28 inches H2O.
OEM Head gasket is 0.0475 crushed. Tops of the pistons are 0.040 inches down in the magnum block
The Magnum has a 9.58" deck height, old pre-magnum spec was 9.60".
Richard Holdener is doing a Dyno test on a stock junkyard 5.9 Mag.
Dead stock without running the pulleys and a short head pipe without mufflers got 288 HP @4K'ish RPM and 399 Torque