your factory intake is a high rise.
i had a 4.3 originally in my truck.
all we really did to if before going to the 355 was bored it .030 over, flat tops, lunati made a good cam for power under 5k rpm.
then slapped a holley 600 on top, and ran 2.25 exhaust with flowmasters.
i can tell you from personal experience that it woke it up to say the least and pulled really good ( car hauler with camaro race car.)
but going V8 and you will think why did i ever build this thing in a full size truck.