The slightly oddball 73-75 K5 Blazer had a full removable hard top. I believe that these were factory equipment (as opposed to 69-72 Blazers which were optional) but I'm wondering about the C-pillar area of these tops. The MPC 75 Blazer kit has a rather significant overhang seam extending from the top of the side windows. At first I thought this was a molding error and was figuring out how to correct it, but upon searching my favourite reference material (eBay motors) I've noticed that some trucks do indeed have this overhang but some appear to have a smooth transition like the 76-91 tops.
Here are a couple smoothies:
And here are a couple with the overhang:
Is this perhaps a difference in top suppliers? Not sure if GM produced these tops in-house or if they would've been farmed out to a specialty shop (perhaps one of the reasons for a switch to simpler half-cabs in 76). I had also thought that it may have been a development progression as the model years when on, but of the examples pictured the smoothies are '74s and the overhangs are on '75s. Then again, by now the tops could be from who knows what year. One common trend I have noticed is that on trucks that have a painted top the overhang has been smoothed out. Given that to paint the top the factory textured coating has to be sanded down this is not surprising.