Help!

[Heydanl]

Hi all,
I am in need of assistance. I have a project Blazer that has the firewall/windshield frame/A pillar (I'll call it the front end for simplicity sake) separated from the bed, there is no floor. I'm in the process of putting it back together but I have no idea where the front end sits in height in relation to the bed. I have no top to establish a top point. Would someone please put a long straight edge on top of a bedside that runs the length of the bedside and extends out to the A pillar and measure from the Centre of the cowl or front fender bolt holes on the A pillar to that line? This would give me a proper landmark that I can work with. I would VERY MUCH appreciate any help here, I'm completely stalled out until I can get this sorted. Thank you in advance!