Reply to "Cam Swap with Motor in Car Possible?"

...Pull the Engine!! You'll be Glad You Did! Much less Hassle in the Long Run. It would be very difficult to 'Absolutely' Seal the Oil Pan and Timing Cover Back On! You will Not be able to get in there and scrap the old Pan Gasket off, that You Damaged when You Broke the Pan Free (unless you Raise the Engine quite a bit, and then Your Halfway to Pulling it anyway). You'll have Oil Leaks Forever!!

Joules, Why would He have to Pull the Heads? Unless The Heads need Work. Yes! I agree, a New Cam warrants 'Freshening' the Heads Completely.

If Your Just changing out the V. Springs; You don't need Compressed Air, either, to hold the Valves from Falling into the Cylinder! You can do an 'Old School' Trick to hold them in Place:

You use a piece of Small Diameter Rope, 'Water Skiing' Plastic Rope works well.
You bring the Piston in each cylinder down, By Hand, Insert about 10-12 inches of Rope in through the Spark Plug Hole, Bring the piston back up (by Hand) crushing the rope against Both valve Heads. Then use Your 'Lever' Spring Compressor to remove the Locks/Retainer/Spring. Install the New Parts. Here's Your chance to Install New 'Valve Guide Seals'. When done, Lower the Piston and pull the Rope Out. I've used this method a few times, it Works!
I just don't care to lean in or have to climb into the Engine Bay to do this kind of Work!

Weather You decide to 'Pull' or Not
Good-Luck with it!