Got a hydroboost repair kit from Restoration Perfomance Center in Arizona. They had the best price.
These input rod seals have to stretch over the threaded rod and piston and not get torn up. They have to stretch a bunch... I made a two part tool with a sleeve and taper piece. The sleeve slides over the threads and end of the piston keeping the seal protected.
Sleeve and taper tool parts.
Got them on OK. Old seal on the sleeve.
The old seals tore stretching them to get them off.