I'm very happy with the engine performance. The motor started within moments of having fuel available to it and proceeded to purr like a proverbial kitten. The motor is the good old 7:1 low compression head, stock as can be. Since I had to replace the motor anyway, I briefly entertained a high compression head, not to mention doing something with the m130 short block that came with one of the trucks. Now that I've had some time with the 404s, I'm pretty happy with the stock performance. The LC crate motor was very cost effective, not to mention a pretty 'plug and play' solution. I realize a HC head or the m130 would have been relatively simple changes (especially the head), but I didn't think the extra expense and time was worth it to me. I'm still playing with finding the optimal timing on the new motor along with the appropriate main jet for Denver's altitude and current weather conditions. At the moment, the new motor seems to like 14 degrees BTDC and 140 main jets. One of my trucks came with a MB rebuilt engine (.5mm over) that really performed well, much faster than the other Mog (the one with the bad motor, imagine that). I'd say the new motor is definitely on par with the other m180 that always struck me as being 'fast'.
A note on timing and jetting: I had read that m180s can like very different timing settings. I have certainly found this to be the case. The MB rebuilt motor was timed by the previous owner at about 22 degrees BTDC (points) with 130 main jets in it. As I said, this motor always struck me as running perfectly so I never changed these parameters. The 'bad' motor seemed to like about 18 degrees BTDC and 140 mains. As I said, the new motor seems to like 14 degrees BTDC and 140 mains.
A note on cooling systems: One of my Mogs has the old style cooling system, one has the new style. Different thermostats, radiators, and plumbing. I found that the old style cooling system was very easy to bleed (self bleeding, really) but the new style took a little bit more effort. It took a couple of sessions of 'burping' to get all the air out. With the install of the new motor I installed the fan spacer, which brings the fan closer to the radiator to improve cooling and a smaller pulley to drive the water pump/fan faster, also to improve cooling. The Mog that had the new motor put in it had the old capillary tube type temp sender/gauge which was faulty, so I replaced that with the temp gauge kit from EI. Nice little kit.
I used camper/RV jacks to remove/install the radio and fire boxes. These also came in handy for dealing with the cabs to a certain extent. I found the jacks on craigslist, trying to keep things on the cheap. One pair is rated at 800lbs each, the other at 500lbs each. The set of 4 came in around $240, a little extra with some new cable. If I had lurked a little longer on craigslist, I'm sure I could have found better deals on these. Each jack lifts/drops independently, so having a second person around to help balance things was definitely good, although I did have instances where I had to operate the 4 jacks myself and everything went well, just more running around. The jacks were great from going to a very low height (box on the ground) to high enough to drive the Mog under a box for mounting. Just wide enough to get the Mog in/out from under the box. It was kind of scary having a radio/fire box up that high in the air, but with each one of the jacks having a tripod base of one sort or another, it was pretty stable.