chevrolet th350 auto transmission changes gear late..?

[pyp5y]

I have a pick up truck running a chevy engine and box- the engine is the old (poss 80's) V8 diesel 6.2 (i think) with a vacum pump where a distributor wouild be on the petrol engine-this pump is connected to the auto box via rubber hose and makes the gears change-3 speed- however it changes gear late--question- is there any way to make it change gear earlier.?

 

[chevyman]

shift kit street or strip th350 $39 www.summit racing.com

 

[Lawn Gnome]

It is called a shift plate, rather easy to modify or install.