At the end of the day, it boils down to what you want out of the truck when it is done. A 70-ish year old truck drives like one. They were not built for comfort, they were built to work.
If you are wanting to fix it up and use it as a truck (hauling, towing, etc), then going with a lighter weight front suspension will not be the best option. If you are looking for a fun cruiser with modern amenities for carrying half a dozen 2x4s or your cooler to the beach for the day, then it would be just fine and gives you an off-the-shelf path to better suspension, brakes, and steering. The tradeoff is that it will lower your ride. Do you consider that a pro or a con?
Contrary to Hot Rod Lincoln's comment, the Mustang 2 wasn't a subcompact and the kits available today are nothing like what originally came on them other than the basic geometry. That said, they are designed/built for lighter vehicles than a loaded truck. I am assuming you have a 3100 since you don't say and those are the most common. From the GM Heritage documentation, that has a curb weight of 3217lbs compared to a Mustang 2 curb weight of 2822lbs. That is not a huge difference, but it only applies when the truck is *unloaded*. If you put 1500lbs in the back or a trailer behind it, suddenly it is a whole different ballgame.
I looked really strongly at doing the M2 IFS conversion for my 58 and talked to all of the kit manufactures that I could find (POL, Strange, Chassis Engineering, Johnny Law, etc) and found pros/cons to their different offerings. At the end of the whole thing I decided that I still wanted to be able to use my truck to haul a full load of lumber or gravel when it is done, so I am going a different direction with it. I don't think that the IFS is an inherently bad choice, it was just not the right one for me.
Feel free to PM me if you like. Also maybe take a look at Coilover's posts; he has a shop that does a lot of these kind of conversions and has posted some really good info.
