cam/brain help

ok need opinions on cam selection...

Combo:
505c1 RB
12.6-13-1 depending on how much I want to mill the heads.
Indy sr's 325 at .550 lift they back up over that to 307-309 at 600 plus, Max wedge port. I will look at the back up issue soon.
440-3 1050 Dominator
2344 bob weight, SRP flat tops
ladder bar Dart sport 4.56 29" tire 8"treemaster.

cam 1 274-280 108 .643 lift Howards solid.
cam 2 280 284 108 .659 lift Howards solid.
cam 3 275 275 106 .620 lift mopar solid
cam 4 279 283 106 .617 lift lunati solid
cam 5 279 287 110 .650 lift Comp solid

what you all think?

I would put cam # 3 in it due to it probably having more bottom end
I would install it so the intake lobe center was in at max lift from 100 to 103 after top dead center, advanced from 3 to 6 degrees from straight up
Isky use to sell a cam that was very similar in lift and LSA, it flat worked great in stock stroke 440 motors with the M.W. heads, stock cross ram intake and dual 750 CFM stock carbs

2 or 5

#1 or 2 SRs have a good ex port

The MP620 cam actually measures out at about 283@.050, not 275.
You didn't specify what rocker ratio you'll be running.
With 1.5's I'd use #5.

Some SR's I tweaked recently:

Lift------int
.100---72.5
.200--153.6
.300--213.6
.400--270.0
.500--314.1
.600--338.4
.700--354.1
.800--357.1

OK ordered #2...Wheres a good place to start looking at the back-up on the flow? Valve job, chamber or port? Should I cut the seats first? Its a stock Indy seat cut right now.

The short-side radius.

But...... Do the valve job first.
SR's are pretty finicky about the transition from the bowl to the seat.

This isn't where your problem is with the flow dropping off at high lifts(that's almost certainly the short turn), but it can have a noticable impact on the final results.