Matt, I just got back from a small IPMS show in Sharon, PA. I've never been to this one in particular, but I will go next year again. I didn't have anything completed to enter, but put the '64 pickup on the table as "display only" per the organizer's instruction. None of the IPMS shows I've been to really tailor to automotive builds all that much, but this one had a pretty impressive (compared to other IPMS shows) car and truck (civilian) turnout. As you say, it seems that they normally cater to the military/armor/aircraft builders.
I know your Blazer is already a show winner, and your recently completed Olds looks to be also, so don't be discouraged by this one show...
To those that may know, isn't this the main reason the NNL was formed back in the 80s???