The 325HP 455 with the #66
heads, big valves, are shown to have 8.2 compression with a nominal chamber specification of 111 cc's. Most are slightly larger and you will see 114 cc's as a general rule.
As pointed out, you really don't want to go higher on the lift than factory unless you add matching valve springs and make sure no interference between valve and piston top. Adding more pressure could accelerate wear on parts that may already be worn - without knowing the condition of the engine. I suppose a compression test or leak down test would give you a much better idea of how well the rings/valves are sealing which would indicate the engine's condition if you don't know. BUT, with everything else you stated, your engine may already be rebuilt?
You also did not state if you were looking for a flat tappet cam or roller cam? So assuming flat tappet cam is your choice.
If the engine has been rebuilt, then I would take advantage of the low compression and install a cam that will build additional cylinder pressure. The Competition Cams with their 110 Lobe Separation Angle (LSA) will typically build additional cylinder pressure (or most any cam with a 110 LSA). The mention of fast closing ramps and valves slamming seems to be a relationship with higher lift cams as the nose of the cam lobe has to be taller which can sacrifice a less radical closing ramp contour. I used a Competition Cams XE274H kit, matching springs/retainers, and stainless steel valves in my former low compression 1972 400CI (manual drums, 3-speed manual trans, 2 1/2 duals with stock manifolds) and was very pleased with its performance. Pulled real well and plenty of pep. Power peaked at about 5500 RPM's and dropped off sharply - which is just fine for a stock built engine and more RPM's than would be used if going by factory specs. It would be tamer in a 455CI, so might be a good choice as long as it'll pull enough vacuum for power brakes. Can't say as I heard any valve noise from the valves slamming closed, but never listened for it either. After about 25,000 miles of hard running, the SS valves and valve seats still looked pretty good to me, but I don't know what I would be looking for as a result of slamming the valves shut.
VooDoo cams are also recommended here, but have never used one. I went with a Crower solid cam/lifters this time around on my 455CI build, but can't give any reviews until I get the car put together and back on the street.
The Summit cams are also well recommended by many. Just want to match the valve springs with the lift and I don't think valve clearance between the top of the piston and valve should be a problem, but it is something to inquire/check into as you begin to go higher than stock lifts.
So cam recommendations on this forum will generate a lot of suggestions. You can also contact a cam supplier as to their recommendation and they will steer you to something they feel will work best.
Assume you have the Performer intake already? Go with a good quality remanufactured Q-jet. Should give you good response and decent fuel mileage.
Just my suggestions thrown into the lot.