which intake to use on stock 318?

I would go with the Wiand Stealth (if you can't get a good Edelbrock LD4B used):


CHRYSLER SMALL BLOCK
STEALTH™ INTAKE MANIFOLD PART #: 8022

View attachment large8022.jpg

Features
High Rise Dual Plane Design
Square Bore Carburetor Mounting Flange
No EGR Provisions
Power band: Idle-6800 RPM
Height: Front 4.88", Rear 5.94"
Port Size: 1.96” height 1.00" width


http://www.holley.com/8022.asp


And run this gasket:

It has the center divider to keep the strong dual plane signal all the way to the carb, and is 5/16" thick which will help insulate some of the heat from the intake.

BASE GASKET PART #: 108-18

View attachment Carb Gask Holley 108-18 lg.jpg


Features
Fit Holley Model 4010™, Model 4150™ and Model 4160™
1 3/4" Throttle Bore
5/16" Thick


These will bolt right up and work with your carb. Do not use a single plane, they are for top end and do not run well for low and mid range street engines.

Are you running a stock cam or aftermarket?

Also, you should have dual exhaust. The stock single exhaust really chokes back the engine. Dual exhaust will give the biggest improvement in performance/economy and will let you take full advantage of the 4 bbl. If you don't add dual exhaust, you're basically pissing in the ocean to raise the water level... Run 2 1/4" duals, and an H or X pipe would be even better.