I used that cam, mostly the Melling version, and Rhoads lifters, with 1.5 rockers, in most all my 455 bracket engines. I always used a Mr. Gasket 2 degree(4 crank degrees) advance key, to make up for timing chain stretch, which happens almost immediately, during or after break-in. Most double roller timing sets have a 4 degree advance keyway. But, I used a TRW stock type set, which had no advance keyway.
I was just assuming that the cam had the keyway in the correct location. But nowadays, most everybody says it's a MUST to carefully "degree in" the cam. I never had the correct equipment or the knowhow to do that. So, me and most other low buck shade tree mechanics just assumed the keyways were correct, and installed accordingly. I reckin my cams were pretty close, since the engines seemed to idle good, run good, make plenty of torque and power, and win races.
I'm not recommending, or even suggesting that anybody should do what I did. But, it worked OK for me.
There is lots of online info on cam degreeing. And there are probably several here who can explain it to you. But, to me, it's not a real simple operation, and requires the correct knowledge and tools.
Just a word to the wise. You may already know this, but that engine makes enuff torque to break the intermediate sprag in a TH400 trans. My 455's broke 2 of 'em. You must have one of the 34 element int sprags, or you'll shift to 2nd one day, and there won't be any 2nd.
I also broke an 8.2 rear end with one of my 455's. You can take a chance & see how long it will last. We got several races out of the one that broke. But, when it broke, it oiled down the track, just past the starting line, and made all the other racers mad.
I switched to a 12-bolt in all my bracket cars, and never had any more rear end problems. Today the 12-bolts are not cheap, like they were back then. If you can't find one for a reasonable price, you might look for an 8.5 out of an early '70's Olds or Buick. But, those are sorta hard to find also. pinion head can tell you all about the rear ends.
Getting set up with a complete ready to race 8.5 or 12-bolt, will not be cheap, unless you accidentally find a real good deal on one that is already set up. So, it might be a good idea to plan to start out with the rear that's in the car, but start looking for a good deal on a replacement now.