Engine combo advice

At 5200ft with your current combo,your Dcr will be about 6.74

-If that was my combo, I would be bumping the Scr up to in the range of 11 to 11.5.
I would be trying to reduce the total chamber volume to 72.5cc +/- .5cc. I would use a fast-rate cam with an ICA of 60*. This may run on 87, most of the time. That could be the XE268H (PN20-223-3).Reducing the total chamber volume with those heads as is will be a challenge.It will take some pop-up pistons for sure.This will get you; 11.32Scr/9.32sealevel/[email protected] leaves a bit of room to go to a smaller cam, but might be a hair low, to upsize. To combat that I would work the numbers using the .039 headgasket. Then if in the future the bug bites for a bigger cam, you can swap in the .028 gasket, and maintain some Dcr.
The cheapest,easiest way to get the Dcr up, is to go to a much earlier ICA.For instance, with a ICA of 42*, the total chamber volume would be 84cc for a Dcr of 8.0. That would be 68head+9.6deck+6.3thin gasket+0 eyebrows. That ICA normally comes on a pretty small cam,(stock type), so you would want a custom grind.
Decisions, decisions. So many decisions.
If you are willing to give up some cam, it will be easier to get the Dcr up. However, IMO, going to an ICA of less than 60*in the Comp line-up, doesnt get you much cam.Furthermore,since you already have the 268H, with the correct 60*ICA, I guess you could give that a chance.But then again since it hasnt been run, Id shelf it.
I also think that with the current combo, that 750 will be lazy. Again, if it was me Id try a 650DP. But since you already have the 3310, I guess you should give it a chance.
If you bump up the Scr as above, the 750 will work much better.
So to recap;I would urge you to install some hi-comp pistons,custom fit into the chambers.Then you can give the 268H, and the 3310, a chance. See if you are happy.
-I realize that everyone is cheering you on with the current combo.And I may be swimming upstream here. I just hate to see you bolt this altogether with the low Dcr, and find out the laziness is unbearable.Then again with an open diff. it could peg-leg its way down the road pretty good.At least until the cross-pin leaves home.
Wishing you all the best