I was thinking about rebuilding my LG4 and putting in some perforemance parts to make it put out about 250HP and 300ft/lb torque. How much would this cost. or would it be better just to get a crate engine or rebuild a 350. I don't need alot of power just decent power. I would like to have HP within the range of 250-300 and torque in the range of 300-350. Nothing big or fancy. Please give suggestions if you have any.

 

Look at it this way....

It's going to cost around $1400 or so to rebuild your 305. For $100 more, the cost of a core at the junkyard, you can have a 350.

Why sink that rebuild money into a 305? If the same $$$$ gets you 50 more HP, there's no reason to spend it on the lesser HP.

"Yes sir, here's my $1500 for a 250 HP 305; and I'd like the free upgrade to a 300 HP 350".

Torque is a function of 3 things: cubic inches, cylinder fill %, and "thermal efficiency" (mostly a function of compression ratio). You can't "build" more torque into a motor, except by changing one of those 3 things. You can move the RPMs at which peak torque (peak cyl fill) occurs up and down by choice of cam etc., but it's pretty hard to change the peak value of it by very much with a given size motor.