[hiccup]

Rather than ask for drawings of the tanks, ask Tiara for the p/n's of the senders, that will give you the lengths you want. The blackwater sender in particular should be significantly shorter than the depth of the tank to keep the float out of the solids at the bottom. IIRC, the recommendation is for the sender to be 2/3rds the depth of the tank for the blackwater.

I assume you aren't just pulling the senders (which is very simple with decent access) and measuring them because access is very difficult? Also, I believe that boat has two freshwater tanks totaling 160 gallons, not 160G/each.