With a 74 400 on stock pistons you won't see anything NEAR 9.5 with a head change. Even with a set of 440 source heads milled down to 75cc you still won't see above 8.5 compression, likely closer to 8.0. Which is still better than your stock 7.5 of compression.

You can get a smogger 440 to perform decent, but your gains will be in:

Distributor tuning
carb tuning
exhaust
cam
torq converter
rear gear.

The cam you are choosing is very mild, a good choice for your compression and gear ratio. Your car will be a good cruiser but not a ground pounding, tire shredding machine. IMO if your stock heads are in ok shape, run them. Now if you were building for 1/4 mile performance, not highway cruising, I would go to a 4.10 gear, 3000rpm stall converter, move up a few steps in cam size, holley street dominator intake(will work with thermoquad), 440 source heads, headers, 3" dual exhaust and you could see some 12 second 1/4 mile times.