Under $4k budget build LA360 build

I'm not saying that you need to install 3.91s.

I am saying that you need to analyze the ENTIRE COMBO.
And if you are on a budget, then you need to put your money where it gets you the most bang for the buck.
And while getting 300 to 350 hp out of a 360 is pretty basic, actually getting to use that power doesn't usually show up until waaaay later in both rpm and especially in mph.............. because the gears control at what roadspeed the power gets delivered.
Now, if you just want a combo that burns rubber, I got nothing against that,lol.