Engine swap advice

Swapping a V8 into a '63 A-body is more difficult than swapping a V8 into a '64-up A-body. The firewall was redesigned for '64 to provide clearance for the V8 distributor and other space-takers; on an unmodified '63 the windshield wiper mount and other areas of the firewall get in the way. It's not impossible; it's been done, but just know what you are up against before you get too far into it. The K-frame won't need changing, you'll just need a pair of '64-'66 A-body V8 mounts. If you want to keep the pushbutton transmission, you'll need a '64 small-block V8 automatic trans; the car's shift cables, driveshaft, and speedo cable will go right onto the V8 transmission. If you do this, be sure to use the 1/8" spacer ring between the larger counterbore of the '67-up V8 crankshaft and the smaller nose of the '66-down torque converter, otherwise you'll lunch the transmission front seal and pump bushing.

If you want to keep the transmission presently behind the '81 318, you will either need to install some kind of aftermarket floor shifter, or swap in a '66 (-only) A-body steering column with shifter. You'll need to use the '63 column-to-firewall mount plate, so some disassembly and parts swapping will be required. Also, you'll need to have a new driveshaft made, since the '63 has a ball-and-trunnion front U-joint that bolts up to a circular flange on the transmission's output shaft, while the '81 has an internally-splined slipyoke that fits onto the externally-splined output shaft of the transmission, and goes to a cross-and-roller front U-joint. You'll also need a '66-'67 speedometer cable to connect the later transmission to the early speedometer.

You'll need to convert from the car's present rotating-rod throttle setup to a cable-type throttle control. You can either hunt up '64-'66 V8 A-body (plus '65-'66 slant-6 factory A/C A-body) parts, or get a later-model suspended accelerator and bracket and drill that onto the '63's firewall. You will also need to make provisions for the V8 kickdown linkage. Obviously you'll also need to have exhaust pipework done.

All of the above is just to get the engine to fit in the car. You'll also need to think carefully about the capacity of the brakes, suspension, and cooling system on the '63.

Unless you're burnin' to have a V8 engine in your '63, seems to me it might be easier and less frustrating (and less costly) to figure out why the \6 is running poorly and fix it. Tell us more about the carb; is it really brand new, or is it a "remanufactured" item? Have you checked to see if the engine's running on all six cylinders (but poorly) or if one or more cylinders aren't firing?