Not a A-body but a couple of questions about a 318.

Hello everyone I am new to the site and have a few questions about my 1984 Dodge D150. Its a 318 with a overdrive 833 tranny. Its bone stock, has been converted over to a regular electronic ignition. It has 2.94 gears in the 8 1/4 rear. My questions are if I was to put LD4B intake on the 318 and dual exhaust would I see a nice power gain? Not looking for a power house but would like to pick up some power! Also could I run newer magnum style exhaust manifolds on this motor? And how hard would it be to change the gear ratio to a lower gear and add a suregrip to the 8 1/4 rearend? I have never dealt with a 8 1/4 before only the 8 3/4. My Dad was the one with all the knowledge and know how and sadly he passed away in November, so I am going at this alone. I may put a 340 cam in the 318 to, but my first actions will be dual exhaust and a 4-barrel. Any help and tips would be greatly appreciated. Thanks
1st of all, sorry to hear of your loss. 2nd, Welcome to the forum. 3rd, I like your trucks, and your ideas are spot-on.