Diesel Bombers - first time modding my cummins need help

Ok first of all I have spent the last few nights reading everything I can on modding my bone stock 1993 cummins and it makes my head spin the amount of contradicting things I read.

My truck is a bone stock 1993 4wd auto club cab with 276k and slowly climbing. I just pulled my motor this week and did a reseal due to a split tappet cover seal and a weeping head gasket at the front corner. I went with a stock cummins head gasket from cummins no aftermarket for that one. the rest I went with felpro gaskets. the motor looks great and isn't leaking from what I can see. I went with the Delphi piston style lift pump as I don't have any mods but I did try a 1/8 timing bump and that made the truck even more gutless. I am sick of it.

I love the fuel economy but want to make more power. now I don't mind if the fuel mileage stays the same with what ever mods I can do but I cant have it go down. empty I am getting 14 around town going to the store and 18 on the highway empty doing 70. now I tow a open car trailer it weights 1500lbs and the cars I tow are anywhere from 3500-5500lbs it does the job but hills suck now I know my converter has a lot to do with that but I will handle that next year when I get some more car cash to play with.

what can I do to improve power and maybe even mileage if that's possible. I am not one to just start turning screws for the hell of it and I keep hearing about the power screw but am worried about a runaway. lets see if some of you guys can point me in the right direction. I have been working on classic cars for a long time now. this is my first cummins and I love it and it has treated me so well in the 6 years I have had it but now its time for a little more.