1st - 882 heads make good door stops and boat anchors. They are pretty much the worst head that Chevy ever used. They were designed for a purpose, none of which you appear to be interested in. Any money put into them is wasted unless they're being used for Grandma's daily driver used for getting groceries, going to Church and Dr. offices.
2nd - to make a recommendation for heads we need some build info including piston cc, piston to deck clearance, rod length, exhaust, cam specs (cam number will help locate all of the specs). You can't just swap heads with no concern of cam or piston volume. Everything needs to work together to meet a goal. Since you have the short block freshly built with a new cam, now you need to pick a head that will work with your cam. Vortec's are a great upgrade if you can find a set that are in good condition, repeat if. But there are many other upgrades that end up being cheaper unless you already have the different bolt pattern intake and self aligning rockers.
3rd - nothing is going to make transmission faster other than more power in front of it. Your rear gear ratio is the ultimate in pathetic.Made for one use only - low power applications that are going to run on the highway with a 3 speed transmission with a mpg goal. You need to sort out your motor and determine what trans and tirer you're going to stick with and then come up with a proper gear ratio and stall.
Lastly, you need to give a better description of 'engine maxes at 3K RPM with pedal slammed'. Will it not run over 3K on the highway, or from a launch, or what?