If your Colt has a standard spur hammer and you install an upswept safety, you'll need to use a compatible ring or rowel-type hammer. You may get lucky and get one that'll drop in and work, and you may not. It's a crapshoot.
Now for the unasked, usually unappreciated advice section.
One...the frame blank was never intended to be a permanent part of the gun. The original intent was to allow trigger smiths to check progress on their work without the hassle of removing and replacing the Series 80 frame levers a half-dozen times. They're soft, and the holes become flanged with use, making it necessary to dress the flanging with a file about every 1500-2,000 rounds or risk dragging on the sear and causing failure to reset properly...which leads to hammer follow or burst fire. Replace the blank when it needs its 4th dressing.
Two...If you remove the Series 80 parts, I strongly advise against letting anyone else shoot the gun.
Should that person have an idiot moment, and shoot himself in the foot....even though the missing parts wouldn't have made any difference...you open yourself up to a ruinous lawsuit should that fact come to light...because you've altered or disabled a designed-in safety feature.
Think your best friend wouldn't dream of suing you? Think again.
When his long-term disability runs out, and his employer terminates him...and he can't meet his mortgage and car payments without robbing his kids' college fund or his retirement nest egg...your assets will start to look awfully tempting.
A civil lawyer's job is getting money for his client, and he will use any and everything at his disposal to do that. Removing a safety would be presented as reckless disregard. That won't end well for you, the defendant.
Just my 2% of a buck.