I just put this LED/LCD in mine. It came with a horrible 17" LCD that was way too small and fairly terrible in every way. I'm using this 24" LCD and it is working great. I absolutely love the image. I used the monitor settings and the CGA to VGA converter board to resize the image down a bit, otherwise it would be too wide. I like the 24" monitor because it gives me more height. I still have some tweaking with the positioning, but overall I love this monitor. I looked at a few, and this HP monitor had the best black levels at a very good price. I also like the adjustments that it had for resizing the image. It also has 'save state' built in, so it turns on automatically when power is restored. Not all of the do this. Still not as good as a CRT black level, but I love it.
HP - 24f 23.8" IPS LED FHD FreeSync Monitor - Natural Silver
I got it from Best Buy for $179. It's on sale now. Once I get the positioning just right, I'll make a nice black poster board surround to block out the sides of the screen that are not used when the image is shrunk down horizontally.
I looked at the 19" LED 4:3 drop in replacement type of monitors, but they were just too small. From what I've found, a 19" LCD arcade monitor is smaller that a 19" CRT as far as image size. I'm not convinced that the images would line up properly with the targets. I didn't want them to be close, I wanted them to be exactly over the right targets. Maybe I'm OCD about it, but if I can make them line up perfectly, why not do it? The 24" monitor is giving me lots of room to move around and tweak the image to get it just right.