Maximum rpm for SB

To lighten your A Body, remove the old carpet and insulation from under the carpet. Insulation weights about 50 pounds. Aftermarket carpet is lighter than factory. Power steering can be replaced fairly easily with a manual aluminum box. That does require some new steering components. Since A Bodies are fairly light to begin with, the steering will still be OK. Saving the weight of the pump and super heavy cast iron steering box is more than a fiberglass front bumper.
Since you obtained a 4 speed manual, go with the 4 speed cam Dodge used in the 340. It is a step and a half larger than the stock 360 cam. Cast cranks may be good for 6000+ RPM, but we set our shift light at 5200 - 5400 on our 318 in a Dart Swinger. This way we are still making good power and won't have to rebuild the engine for a decade of street and strip. Have a qualified shop set the spring height for your cam when they do a valve job. Show the shop the cam specs. That way you will avoid valve float. Headers and an aluminum intake will save you another 50 pounds. If you are taking the car to the track, move the battery to the trunk. Do that when you have the carpet out. If you have a bench front seat, replace that with a couple bucket seats. That will save you another 20 pounds.