modern 4ch system with 2 ch 8 track?

Hi guys/gals, new to the board with a unique problem that I have not found a solution to in my searches here.  Thanks for your help in advance.

This is going in a 1969 classic car:  original converted AM radio with modern AM/FM/IPOD guts, HU fronts are 4 ohm speakers and HU rears are RCA.  I have a Alpine MRP-f200, a Kenwood KSC-SW10 powered sub and a vintage realistic 8 track 2 channel, 8ohm, 12w total (for that day-2 look ƒº).

This is the plan:  all 4 speakers (infinity Kappa¡¦s) are run from the Alpine.  HU fronts go to ch1&2 line level inputs, HU rears go to ch3&4 RCA.  Sub is hooked up normally to pre-outs.

Amp and sub will be hooked up to the HU¡¦s remote on.

Now here is the problem.  I need/want to run the 8-track through the Alpine amp.  I plan on a separate remote on switch for amp and sub when the HU is off and the 8-track is on.  I know I could run the 8 track to the ch3&4 speaker level or use a LCO to RCA ch 1&2, but I want all 4 speakers. ƒº

Is there a way I can splice the 8ohm/12w/14V 2 channel 8track to both the Alpine speaker level inputs and LCO to RCA at the same time?

I have seen the source switches, but the ones I saw were all 4-ch and I would have to use an LCO to RCA, then 2 RCA Ys to the switcher.  I think that would work, but it¡¦s a lot of gear to fit in the small space that I have, plus I would like an easier (cheaper) way.

Thanks, Kevin