Intro P10 kurbmaster reefer gears

[Bldr]

Hi I've been lurking for a while and finally trading my Chev express for this 73 Kurbmaster JR/p10 (pictures below). Being doing some work to get it road worthy again and found out the control arms are actually from 72...Dash looks pre 73 as well, so I'm posting here.

The rear gears are 4.11 and can't quite get up to highway (80km/hr) with a 292 and th350. I've searched and searched and thought the 3.08 might be better, but am wondering with it loaded with my tools it might be too sluggish taking off. I mostly drive city, but highway is normally 110-120km/hr 68-75 mph...Am i making a mistake with the 3.08 gear? Any one else put them in their p10?

Thanks!