The Comp Magnum rockers 350 lb limit is max open pressure allowed, not max spring rate allowed, the Isky springs is 320lbs open so it is under the limit. The Howards spring is nearly the same, so you have no worries there.
I'd probably use the TM-1 on the smaller engine and try it, if it didn't run the way I thought it should then try a Holley Strip Dominator or Weiand Team G.
The 327 will just make slightly less power than the same parts in a 350, just because it has fewer cubes. Expect the stall to be a little lower due to the engine having less torque. You'll definately want to rev it into the 72-7300 area for the shift point.
I'd stay with the same camshaft ideas you have been looking at, they will have a little higher powerband than listed as listed values are based off of 350 cubes. This works out fine since you are going to have to rev it up to really get into the meat of the power anyway due to the short stroke and small cubes. Good thing you do have that 8" converter, now you will really need it.
Got a casting # off the block?? Wondering if this is small journal or large journal. Would be a very good idea to have ARP bolts put in the rods and have them resized if they don't already have them.