what is the best way to rebuild a 305 with more horse power the motor now has 170000 miles on it and when i hit the gas the oil pressure drops instead of getting higher and i want more horsepower

i'd guess a std over bore rebuild...

is it FI or carburated?

this should be in the "tech section"

best way? tie it to a chain, use as a boat anchor and buy a good 350 4 bolt main block, more parts for them, and they are built strong

Like what SS said

I'm plagued with the 305 too.

It only makes 185 HP and 255 ft lbs of torque. the Carburated one makes 205 with 275 ft. lbs. torque.

The easiest and cheapest thing is to get a key ready 350 from GM performance parts i think for 330 hp its about 4,000.

However if for some god awful reason you want to keep the 305 Edelbrock does have a Intake for it but then you would have to switch to a carb and that would be too complex since you would have to change out the entire fuel system. There is Camshafts you can get and you can send your heads to a machinist to get them polished and widened.

SO the right thing to do is If you have a Th 400 or Th 350 trans bolted to it take them out and put them in a bad ass go kart. Buy a Create 350 and TH 200-r4 trans. Trust me that overdrive will save 10 fold in gas mileage.

trust me I have looked and calculated to mod a 305 is pointless. just go for a 350.

As for the oil gauge it could be the sending unit or bad gauge. But if its normal drive it till it dies. A rebuild might not be needed. All you can do is add K & N air filter. and drop in a cam and run premium if you want some more horsepower.