340 intake on a 318?
According to an old Chrysler guide for A engine modification printed in Hot Rod back in the 70's :
Step 1- Add headers and good low restriction dual exhaust.
Step 2- If working with a 318, install the 4-barrel induction system from a 340/360
Step 3- Lighten the car
Step 4- Add MoPar D.C. electronic ignition kit (part No. P3690426). If car already has electronic ignition recurve distributor and use D.C. control box.
Step 5- Upgrade fuel delivery system. Install Carter No. 4594 electric pump (P4007038) at rear of vehicle. The high-output mechanical pump(P4007040) may also be desirable.
Step 6- Install 4.10 or 4.30 ring and pinion. Adding 9" slicks mounted on 7" or 8" wheels for strip use only is also recommended.
Step 7- 318 engines should be fitted with the 340-type hydraulic cam and valve springs (part Nos. 2899206 and P4120249 respectively)
Step 8-318 engine should be fitted with 340/360 cylinder heads.
I believe this was all in the Direct Connection book as well.