Are you asking how much horsepower is lost when you remove the stock TBI and replace it with a 4 BBL???
A stock '87 with TBI had 210 HP @ 4000 RPM and 300 FT/LB torque @ 2800 RPM in the 10 and 20 series without heavy duty chassis.
20 series with heavy duty chassis and all 30 series had 185 HP @ 4000 RPM and 295 FT/LB @ 2400 RPM.
All specs are SAE net.
Mike <img src="http://myweb.cableone.net/m-t-w/83chevy/silverado.jpg">