Very difficult to tell from the pics. The DODGE RAM logo on the side of the truck would tell ya, but I can't zoom in enough. The 12V just say something like CUMMINS TURBODIESEL but the 24V's add 24V to that.
I think all '98s have the same 'new' interior, didnt matter about the engine. My 98 12v looked almost identical to my '01 with a few minor things; 98 has the old pull knob for headlight w/o fog lam. The fog lamp is a square push button over onthe RHS. The later models had a storage cubby on the RHS of the dash.
But the VINs are different for 12V and 24V. The truck you posted is 1B7KF23D6WJ133706...8th digit is 'D' = 5.9 Liter I6 Diesel...12V
If it was '6', that would be 24V http://www.dodgeram.org/tech/specs/VIN_decode.htm
98s came in three configurations. 12V extended cab (no rear doors and old interior), 12V Quad Cab (New interior and rear doors but still had 12 valve, these are very rare and very sought after, the only year that a 12V Quad Cab was built), and 24V Quad Cab.