All if the GMCs are good street engines. Bill Fisher really liked the 248 for street builds. I had a 248 in my pickup while I was building the 270 because at the time I could not find a 302. For a driver you would hardly notice the difference. The shorter stroke has some advantages. Someone with an honest sense of how their engine will be used might be interested in your 248 stuff especially if they like turbos or superchargers.
There are iron & steel cams that call for different distributer gears. I have a couple of NOS cams. I don't know how to measure them other than lift. I can not remember the details but all the info you need is out there. There is a ton of information in old posts on this site if you can learn to use the search feature here. A lot of it posted here by some of our long gone members who helped develop the performance side of these engines.
