I've owned and raced a lot of different M.W. motors and cars over the years at variuos altitudes,NHRA stock to S/G, none above 5500 Ft elevation though. I would look at a solid lifter or solid roller lifter cam that had between 250 to 270 degrees duration at .050 lifter rise and as much lift as you can get Have it ground on 106 to 110 lobe seperation angle, more duration wider LSA, and install it with between 3 to 6 degrees advance on the intake lobes.
I use to use a lot of Isky cams, my favoriite solid lifter grind is not in thier catalog anymore, it was thier old .590/616(EDITED) grind, they would probally make you one as a custom grind now. It was ground on a 104 LSA and it had a bunch of bottom end and would usually quit pulling hard around 7000 RPM with the bigger Stage 3 heads, intake and carbs like you have IHTHs
There are a lot better cams out there now, I like and use Comp Cams and Bullet Cams for most of my builds now starting back around twenty yrs ago