Help cam problem in a 440

The Comp 305H doesnt spec single springs...Soi there are a couple problems. First, not knowing what you have for singles, I'm using the comp number 911s as an example. It's similar to the MP "Hemi"type single spring with dampener. If you have stock single springs, your builder should find another line of work.

The cam specs the Comp 924, which is a double spring with a dampener. It requires the spring seats be cut flat (removing the step that indexes the stock oor single type springs), and the guide to be milled down and narrowed to use the small positive type valve seals. You cant run double springs without doing that. At least not for too long. Nowadays, the oil issues and break in procedures say to keep the inner spring out during cam break in. That would have been on the paperwork if you bought a cam and lifter kit, as opposed to the cam and lifters seperate. Some shops dont bother, some guys dont like to have to go back in and install the inners later. I dont mind the extra level of safety, so that's how I do all my break ins.

Assuming you used a typical 911 type deal...You have a couple things. The spings are designed to be able to accomodate a certain amount of lift. In the 911s case, the coils hit each other when using Comp type retainers at approximately 1.200" as measured from the spring seat to the top of the retainer. They are installed (or recommended by Comp) to go in at 1.900, but I find most going in around 1.8-1.85 using Comp retainers, new valves, seats, etc. That would give you .600" lift max before coil bind. Plenty for that cam, which has 525, minus the usual rocker ratio and angle losses. It should be tall enough to accomodate your selection. But, the tension is way too light. Like 15% too light. In terms of RPM, tha means 5000 rpm vs 5900. And really, it's much worse than that, because bad harmonics caused by the lifter not following the cam will hurt you way before that. The 911s reach peak tension at .350" valve lift when installed at 1.85. The 924s reach peak at .550. Bad harmonics can cause the lifters to lose the oil film, and then in less than a second, they're trash.
Now on to the lifters. You didnt mention which ones you had. Or if lifter preload was checked when the lash was set cold. There are two types of lifters Comp uses. One is more a stock street type, and is fairly easy to over tighten the rocker adjustment during lash sessions. Those are p/n 822-16, and are cheaper and listed as OK for the cam. Teh number I'd rather use is 867-16. It's a performance "anti pump up" lifter that makes sure the valve train is stable at higher rpms. Using them can also help idle quality in a street car.
At this point, I'd say your engine guy messed up. Whether or not it was trying to fit a budget, or simply a metter of him not building enough Mopars to really know, he should have said "no" to running the wrong springs, and he should know how to set preload to make sure things are safe for you to start it. I've used Comp products for 16 years now, and even with the more recent issues of break in problems, I've had no cam/lifter failures. But I havent ran inner springs since '90 on break in, and I have spots on my assembly sheet for lifter preload and checking for rotation. Many pro shops dont.
As far as the firing and break in...How was that done exactly? How long did it sit before install? how was it prelubed? what oils/any additives used? What oil filter was on it?