How much horsepower for 318?

The missing factor is the comp. ratio.
The missing performance items for the reat is a possible higher stall to get off the line quicker and IMO, I would go 3.55's for the rear gear and a 26 inch tire. (235/60/15) Add HD rear springs. I grabed my springs from http://www.espo.com/
They were ordered 1 inch higher than stock. Gives the car a good looking mild rake.

You failed to mention headers or not. IMO, a set of headers with 2-1/2 inch exhaust will fit the bill well.

The exhaust shot is Hooker comp (NOT super comp) headers and Jegs exhaust kit for A bodies @ 2-1/2 with there muflers. Sounds nice.

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