i have been running stock shocks on my slash since I got it. The only thing I changed was the mounting holes like you did. outside on front and 2 out from stock on rear. I also changed the oils. I was running 40 front and 50 rear and it worked great for me.
thicker oils has got to be the first thing to do if you are on a budget. 40-60wt oils is what almost everyone with a stock slash is running. Some run heavier in front than rear.
Also you could look into changed the springs for stiffer springs a long with thicker oil.
here is a link to springs just go to the traxxas and integy sections. Integy makes a assortment for around 10bucks. Or you can go traxxas.
http://www3.towerhobbies.com/cgi-bin...AdvancedSearch