Resurrecting Aurora R4 ALX

So in a someone's trash is someone else's treasure kind of way I came upon an Alienware Aurora R4,  16G ram,  I7-4820K,  GTX 770 2G x 2 (SLI).

The PSU apparently died and the former owner wasn't interested in fixing that.    The bad is he took the old power supply,  wiring harness and plastic mounting plate that the power supply attaches to. 

(it also is devoid of hard drives but that's easily overcome).

So questions, I have, answers I seek. 

I was debating if I should just yank the GTX 770's out as they are huge power hogs.   Would a single 1650 super be about as good or better?  I think so, but it's hard to get a read on that.

The thing is if i go with an after market power supply, I don't have to get as expensive one if I'm not driving those two cards.

Thoughts on going with a single 1650 vs the SLI 770's?

The other thing is it might be moot, as I can't seem to find the plastic mounting plate. as a seperate item.   So i need to figure out the PSU.   I found a "W299G Precision T5500 875W Power Supply (Certified Refurbished)"  for $85 it looks like it comes with the wiring harness and the plate

I know the power supply for the T5500 and R4 are interchangable but not sure on that plastic piece. It looks right..  (Question out to the seller but haven't heard back yet, good chance they say dunno).   Does anyone here have thoughts on whether that will fit my case?

So my first option is probably to get this PSU and drive the GTX 770's if that fits. If I can't find anything option 2 will be to get a 1650s and lower powered supply and rig something up for a plate.

thoughts?

thx!