Which intake would work better on an RB 499 in an A body?
Specs
9.8 to 1 comp
Homeported 906 heads
comp extreme cam XE290s 290/298 dur with .540/.558 lift
850 carb

I have a Edelbrock rpm and an edelbrock tm7 to choose from.

between those 2,the rpm is better-see if a friend has an m-1 you can borrow-

Try both on the car I have dyno tested both on a similar motor, the RPM has more power below 5000 RPM and the Tarantula has more power and torque above 4500 RPM.

Depends on how high you'll be taking the engine.I'd personally use the Tarantula. Like Cab says...the TM7 will give you more power at the higher RPM's.....Cam etc will have a lot of bearing on your results and you have a decent cam in there. Torque at the low end is NOT going to be a problem with 500 cubes.
People seem to underestimate those old Tarantulas.

Are you running a scoop ? If not the RPM may not even fit. I will say we use the RPM on my sons 400 but you have 100 cubes on him. The RPM was a tad faster then the Holley SD single plane but has less mph.

RPM - 11.55 @ 116

Holley SD - 11.59 @ 117

He likes the low end responce of the RPM better and he takes it to 6500 with the RPM. I myself use the Indy dual plane on my 493 and I really like it but I have max wedge ports. But it does come in standard ports also. Ron

Ordinarily I'd say the RPM if hood clearance will allow and the Tarantula is reportedly a higher rpm piece but with your addt'l cubes the added airflow will come in at a lower rpm than a non stroked eng so the T may work fine. As Cab said I'd try both! With some Permatex #2 in the toothpaste like tube around each side of each valley pan gasket port (my pref on an alum intake/Permatex #1 on cast iron) you can easily reuse it so it'd be easy to swap out

Yes i do have a six pac scoop on it,looks like i will try both.

there have been several dyno test done , depending on what type of engine you have built , can have a effect on which intake would be the best suited for you're engine, i believe it was a hot rod magazine several years ago that done the test.
the rpm and the m-1 are both top of the food chain on those tests,
in all the intakes tested, the results where eye opening,due to the fact that some of the intakes that where 'outdated' actually done a very good job at delivering hp/tq #
the test was also done with dual quads , at which the the m-1 intake out performed several others in that catagory but by small margin,noted that m-1 dual intake is not in production.
Me personaly, ON MY COMBOS , i haven't seen big changes in diffrent intakes on same combos, the best i saw was a tenth,
i ran a tm7 changed to a torqer no gain what so ever! then i someone told me to buy a team 'g' what a wast of money on my combo, lost et and 60 on that one! they must like high rpms.
went from torqer to m-1 picked up tenth , that was it, on the same combo , i now have a rpm, there was a 0 diffrence in it on the same combo, thats on my combo!\

I just got the a body the other day so the engine isnt in it yet.I did have this engine in a 69 coronet that ran 7.64s in the 1/8.At that time it had a wieand team g on it.Torque wasnt a problem with that intake.I plan on using the car mostly for the strip but it will also be driven on the street.Yes i do know the heads are probably not flowing nearly what the engine would like but its what im stuck with for right now.I dont have the coin to get aluminum ones right now.