Yes you can do that (assuming you don't need to dynamically change the voltage within a .tran run) by parameterising the sources and using the table() function to look up the desired values.
Step a parameter run number, and from it generate the other parameter values required :
.step param run 1 3 1 ; middle no. is no. of runs
.param Vac={table(run, 1,254V, 2,264V, 3,274V)}
.param Vdc={table(run, 1,1V, 2,2V, 3,3V)}
then use
SINE(0 {Vac*sqrt(2)} 50) for the AC source and
{Vdc} for the DC one.
Note that the table for Vdc is redundant as run already had the desired value!
The 'V' units in the table() functions are syntactic sugar - LTspice ignores unit letters after a number or number followed by a S.I. multiplier suffix unless it mistakes them for valid S.I. multipliers so *DON'T* try to write the value of a 1 Farad capacitor as 1F as LTspice sees that as 1fF.
The spacing is also used to clarify the input:output pairing
You'll find the table() function documented in the help file at 'LTspice'=>'Circuit Elements'=>'B. Arbitrary Behavioral Voltage or Current Sources'. Input values for each point pair must be in order. It interpolates between pairs (but does not extrapolate beyond the table limits) so you can use a sparse table.
Also note you aren't limited to stepping sources. You can step *ANY* component that you can parameterise its value as a number, even active devices if you define a model for each number! see:
http://ltwiki.org/?title=Undocumented_LTspice#Stepping_a_ModelTo do the same thing *within* a *single* .tran run you need a control voltage source instead of the parameter 'run' and to use .func (which has slightly different syntax) instead of .param with arbitrary behavioural sources instead of plain voltage sources, however generating a table controlled sine wave purely mathematically is *very* slow so one of the other methods of providing a dynamically changing voltage suggested above by StillTrying or Jay_Diddy_B is probably preferable.