speedo wont work with my custom chip

[91camaro_rs]

ok so originally my car was a 3.1 v6, went through 2 305's and now i have a 350.

its a 350 TPI with speed density, has a 7730 ecm, i burned a stock AUJP chip and the prom im using is from a TPI 305 but the chip is for a 350. my speedo doesnt work and i get code 51 which means "PROM failure" how should i fix this?

thanks in advance