I have a 1987 R10 Silverado with the 305 and automatic transmission, Problem is when driving down the road and WOT the truck spits and sputters or bogs down Also when in drive or reverse if given little gas or just idling it will stall out. I have pictures of the motor and electrical i can post if needed. The starter, fuel pump, distrubitor, spark plugs plus wires have been replaced with new.

 

ok, but did you check your timing? how many miles on this 25 year old truck?

 

The timing is a little off i set it myself but, far as miles not sure odemter says 768k miles but the odemeter is also broken

 

if the timing is a little off this could be the cause of your problems.