Ruben the best way to proceed is to create a vector-valued ARIMA process with two components. Then based on this, you can build graphs as follows (replace "rFmode1" with the name of the process you defime on your own:

nssvmean = TimeSeriesThread[Mean, rFmode1["PathComponent", 1]];
spsvmean = TimeSeriesThread[Mean, rFmode1["PathComponent", 2]];
nsmup = TimeSeriesThread[Quantile[#, 0.95] &, rFmode1["PathComponent", 1]];
nsmdn = TimeSeriesThread[Quantile[#, 0.05] &, rFmode1["PathComponent", 1]];
spmup = TimeSeriesThread[Quantile[#, 0.95] &, rFmode1["PathComponent", 2]];
spmdn = TimeSeriesThread[Quantile[#, 0.05] &, rFmode1["PathComponent", 2]];

{DateListPlot[{indices["PathComponent", 1], 
   TimeSeries[nssvmean["Values"], {{2014, 11, 28}, Automatic}], 
   TimeSeries[nsmup["Values"], {{2014, 11, 28}, Automatic}], 
   TimeSeries[nsmdn["Values"], {{2014, 11, 28}, Automatic}]}, 
  Filling -> {3 -> {4}},
  PlotLabel -> "Nasdaq series with 3M projections bands"], 
 DateListPlot[{indices["PathComponent", 2], 
   TimeSeries[spsvmean["Values"], {{2014, 11, 28}, Automatic}], 
   TimeSeries[spmup["Values"], {{2014, 11, 28}, Automatic}], 
   TimeSeries[spmdn["Values"], {{2014, 11, 28}, Automatic}]}, 
  Filling -> {3 -> {4}},
  PlotLabel -> "S&P series with 3M projections bands"]}
DateListPlot[{indices["PathComponent", 2], 
  TimeSeries[spsvmean["Values"], {{2014, 11, 28}, Automatic}], 
  TimeSeries[spmup["Values"], {{2014, 11, 28}, Automatic}], 
  TimeSeries[spmdn["Values"], {{2014, 11, 28}, Automatic}]}, 
 Filling -> {3 -> {4}},
 PlotLabel -> "S&P series with 3M projections bands"]

{ListPlot[TimeSeriesThread[First[#] - Last[#] &, {nssvmean, nsmean}], 
  PlotStyle -> Blue, PlotLabel -> "Stoch CoVar Nasdaq mean difference"], 
 ListPlot[TimeSeriesThread[First[#] - Last[#] &, {spsvmean, spmean}], 
  PlotStyle -> Magenta, PlotLabel -> "Sotch CoVar S&P mean difference"]}

spath = RandomFunction[estPmod2, {1, 90}];
sts = TimeSeries[spath, ResamplingMethod -> Automatic];

sfunc = sts["PathFunction"];
gfunc[t_] := Join[{t}, sfunc[t]];

ParametricPlot3D[gfunc[t], {t, 1, 90}, 
 ColorFunction -> 
  Function[{t, x, y}, (ColorData["TemperatureMap"][t])], 
 PlotStyle -> Thickness[0.012], PlotTheme -> "Marketing", 
 BoxRatios -> 1, AxesLabel -> {t, "Nasdaq", "S&P"}]