#10 irregardless of what ever year 12v motor it is. I can get more power out of a #10, timing and a gov spring kit than any other plate and better more usable power curve.
Depending on if it is a 49 state truck or a Cali truck and what year, the best years are 96-98 12v 215HP 49 state but even a 180/175hp version builds alot of power.
You will definately need a clutch 650 ft/lbs and things start slipping especially when you start pulling.
I would recommend finding a 1996-98 215HP
Put in a Pyrometer and Boost gauge
Check your intake tubing boots they tear by the radiator.
Next do.
4" Exhaust
#10 plate (can be slid forward to increase fueling (HP) after installation)
3000 rpm gov spring kit
Timing bumped to 16-16.5*
no higher youll be pushing the cylinder pressure and head gasket at 16* I ran 17* fo along time no problem and towing but 16* seemed to be a good sweet spot.
Look a Htturbo.com, they have a reasonably priced Hybrid 60mm stage 3 modification for your turbo add that with a 14cm WG exhaust housing (spools fast with the big intake fan, stock is 12cm watsegated, the 14cm lowers exhaust driver pressure from that of the 12)
Or a 16cm non wastegate housing (spools slower better with injectors, lower yet on exhaust drive (back pressure) pressure).
If you arent towing all the time and want the snappy horse power go with the 14cm you'll be happier, I towed witht he 16cm and loved it but many people who drove my truck didnt like the lag.
I suggest the turbo modification because of how well it increases the efficiency range of your turbo and helps cool down your EGT's, a 215 pump with a #10 runs warm especially with towing and is at the outer limits of the standard HX35, the modification extends that range and allows you to slide it forward and capitalize a little more on the potential power available.
Those mods with the timing will yeild you a fairly well ballanced setup that will push good snappy numbers tow well and leave you extra throttle to play with. 370HP aka. marine injectors are overkill until you want to jump up in turbo's to a B1 series or a HT2B or Twins