lo po cam dilemma

Now you're half way there. And I can already tell you that

It is my opinion that with just 8.9Scr, both of those big cams would have been very soft on the bottom. The Dcr would be 6.5ish with cylinder pressure of near 122psi.Can you say; disappointing?
For a strong bottom end to pull those 2.76s, with just 8.9Scr, you are gonna need a very early closing intake valve, to trap as much of the charge as early possible and compress it for as many degrees as possible. Some RV cams do just that.Perhaps yours is one of those.

As an example;A cam with an ICA of 50 degrees might bump your Dcr to 7.8 and cylinder pressure might climb to 155
I must warn you tho that a 50*ICA is a pretty small cam and will be done very early. This is not necessarily a bad thing, cuz with 2.76s, 5500 at the top of first gear will be speeding, just about anywhere in Canada. And with 150Plus psi, she would be snappy, hang on tight!

I did a little math; to get a 50*ICA might require a 252/262/108 advertised cam,in at 104.If one can assume fast ramps this might be;212/222/108 at .050. now compare this to that 6400Summit at 214/224/112.....See what I mean about that 6400?;all bark,no bite.