I half-buried and leveled in the gravel some treated 6x6 sections across the alley and use a Tru-test platform "Alleyway" scale just ahead of my one chute. Has worked well for almost 10 years. Be sure to pin the load bar mounting holes to the 6x6's with nails or screws etc so the loadbars don't slide off of the 6x6's. Tru test has good waterproof wiring and capped connectors so I leave the platform and loadbars in place year around and take the scale indicator inside the shed when not used.  The platform and basic EZweigh indicator head is a good, cost-effective combination that works well for widely varying, often moving livestock.