Mopar Cam 284/484 or 288/497

Well, I wouldn't spend the time to pull out your 280/474cam, to install a 284/484/108
So for me it would be the 288.
But for a streeter,
I would leave them both in their boxs.And I wouldn't be advancing them either in an effort to pull up the low-speed; I would be upping the stall, but not into the 3200up zone! And I would be using 3.55s to 3.73s max. And I would keep the dualplane, and a DP carb. That's what I would do for a streeter.But I would be running the Dcr up to the max, for your elevation.

But if you already have 3.91s and whatever induction, I would stick with those. But I sure do love my DP carb! 3.91s will cover a multitude of insufficiencys.
I have just a 270/.549/110 Hydro-cam and it blows 325/50-15 Drs to smithereens, with a 10.97 starter gear in a M/T. So I gotta ask, what are you trying to achieve?I mean it looks like you are chasing a few horsepower at 5800, and willing to give up quite a bit of driveability to get it. Ima thinking you might be a lil short of compression?

Depending on the exact engine build, your Scr is around 9/1 and with the 288 your Dcr may fall to 6.77/128psi
To pull off that 288 properly The Scr would need to be about 11.0 to net about 8.24Dcr and 166psi.
You already have too much cam for your compression for a streeter. The new gears and BIG TC will get you through that, but at a horrendous sacrifice.

Simply put,IMO, the KB107s are the wrong pistons for open-chamber heads.And you didn't mention any machining. If you want to keep those pistons, I would recommend heads with much smaller combustion chambers. Then you can back up the bus;use a 8.7 to 9.2 starter-gear,and a 2800TC. This combo will annihilate 275s with a lot less than your current cam, unless maybe you are running SS springs or traction aids. With the current 280cam, you need about 10.7SCr