I use Mega and Spikes lowers for my own rifles but my girlfriend's dad wants his built off a Colt.

I told him that the difference is basically in cosmetic but he seems hell-bent on a Colt stripped lower receiver.

My google-fu is weak right now but after some preliminary searching I'm coming up with nothing.

Where should I look?

They probably don't really exist. Why start with a stripped lower anyway if you're going for Colt? Just sell the stock and/or grip if you want something different.

Buy a complete colt and either add whatever to it or sell off the upper.

specialized armament sells stripped 6920 lowers but they are like 400 bucks. Personally I would find a 6920 which can be had for around a grand to 1100 and part out the gun if you have pieces you don't want. That or one of those used 6520's that have been floating around.

The EE if youre lucky,  honestly...

I'm probably going to do this. He wants an M16A2 clone and it doesn't look like colt still makes them. I suggested a BCM A3 upper but he's firm about A2, so I'm pretty sure I'll end up having to assemble the upper.

I don't recall ever seeing Colt stripped lowers for sale unless they were used and priced out of the world.  You will end up having to buy a Colt and part it out anyways unless you get lucky and find an A2 model at a show or something.  They stopped making them a while back.

PKfirearms sells a2 uppers with the government profile barrel. They have bushmaster and sabre defense barreled uppers. Its like an extra 25 bucks to have them do one with an a2 upper. Past that I'd be on the lookout for colt or fn a2 upper.

Colt 6520 rifles can be had for 900 bucks if you look around. Has an a2 upper and lightweight barrel. I'd buy the complete rifle and pull the stock off and install an a2 stock. Replace the barrel with a 20 inch and call it a day. The lower for them is even marked a2(although it says carbine).

As far as the stripped lower I'd still get a new colt rifle and sell the complete upper and the stock. You will end up about the same but with a colt lpk already installed.

IM sent

This

Finding a stripped Colt lower are a hit or miss, but sometimes you get lucky like what happened to me.

I wanted to have an all Colt A2 clone but the factory was not selling that version anymore, all they have are HBAR rifles, so I decided I'm going to just put it together myself.

Got lucky and found a stripped Colt MT6601 HBAR lower receiver from my local dealer when I was picking up another complete lower half for my other carbine project.

I also found a source for a brand new never issued USGI M16A2 upper half, then all I did was I bought a Colt lower parts kit from Specialized Armament Warehouse (SAW), also bought a new take off Colt M16A2 buttstock group and in about 30 minutes or so my A2 clone was done.

Another way of doing it that cost less would be to buy a complete Colt MT6601 rifle, find a M16A2  barrel assembly and just swap the HBAR barrel of the rifle for the M16A2 government profile barrel assembly, then sell the HBAR barrel to offset your cost of the A2 barrel.