A couple of thoughts/ideas/questions: I think you may have combat issues, as well as spotting issues. but I'll talk about both.
so did your t74's "start" the game by moving onto the board?. Did the M48's attack them as they moved on the board? I wasn't clear on this from your description. If so the m48s may only conduct opportunity fire as they 'see' the t-74's move onto the board (check rule 7.05 page 10) during the t-74's movement if the m48s can see them (see LOS rules pg.8 [7.01 etc])
If the M48's didn't destroy them while moving on, the T74's should have moved into concealing terrain of some sort, if at all possible (and if there's nothing to hide in within 20 inches of their edge of the board well, Do you like your T74s' with some pink or no pink in the middle?)
Make sure you understand which terrain types are concealing and block LOS (see the terrain effects chart (TEC)). Also make sure you know how to use rule 7.01.06 (pg

second, and more importantly an attack is conducted by 'targeting' (identifying) 1 (ONE) stand as the target. Then you declare (and mark with a bead or marker) which stand(s) are conducting the fire. Once marked, they are conducting fire, whether they hit or not and whether the target is destroyed before you roll for them or not) Only these stands may fire on the target during this phase. A cohesion roll 'to fire' is made (applying mods for the terrain that the defender is in, and S and or D effects on the attacker, where applicable - to the die roll result) for each attacking stand. Each success means you go on to the CRT process. You roll 2d6, modified by range, and look up the result and apply it to the target. repeat untill all declared attackers have made at least a cohesion roll or the stand is 'E'd on this one target.
Then its the Soviet's turn to shoot back (as those tricky, concealed m48's on the hill have exposed themselves by firing on comrad Ivan, god rest his soul) or if this is op fire during the movement phase, its the soviets turn to move the next model that succeeded its 'to move' cohesion roll.
By the way, the rule book doesn't contain the range effects chart (oops), but you can get it from the Combat Table Cards link, under the Modern heading of the Free Stuff section of this website. http://www.ghqmodels.com/pdf/GHQModernCTC.pdf
Did this help WHM? Let me know if you have further questions or issues.
regards,
RedLeif