The Smarty is awesome but best bang for the buck I don't know. It's awfully expensive for 65hp. I would have to say either a used EZ for $200 or I've seen Jammer 1 and 2 nozzels as cheap as $150 brand new.

 

As I look back on my upgrades, I would do it this way.
Better torque converter- lower stall, Smarty, 275 injectors or better yet is the Mach 1.6 injectors. Raise the line pressure in the trans to 70psi.
This will give you a great towing truck that delivers good mileage. A better air filter too.
Then, as you get the bug and want more power, a TST PM and 4" exhaust.
Much bigger injectors will force you to start buying turbos or twin turbos.
My set-up still lacks in the turbo area.
I either need to drop down in injectors a size or just go to twins with bigger injectors!

 

Get it right here on DTR... thats where i got mine, and i love IT!!

 

The smart is hard on a stock tranny. If you tow run the fuel and boost mode. As for mods valve body and good torque converter. I don't like low stall converter. They make your truck sluggish and smokey. A edge ez is a cheap bet. A used set of 60 to 100rwhp sized injectors would work well for a stock turbo. A 4in exhaust is nice add on and is fairly cheap. Fuel pump upgrade is a must. A cold air cold kit is good idea. Towing in the summer and killing hills, I seen 200 deg's F. Normal city is around 160's and hiway is below 100. I have a mag tec deep pan and the sensor is on the bottom of the pan. My tranny cooler is kinda beat up and I haven't installed my electric cooler fan. A cheap tranny cooler upgrade is get a heavy duty 1/2in oil cooler. It drops tranny temps and doesn't restrict oil flow.