Yes you can. If you're nor replacing the core you can remove the tees and use straight connectors.

Dennis,
From my phone.
________________________________
From: JRodgers<mailto:jrodgers113@GMAIL.COM>
Sent: ‎3/‎21/‎2014 6:30 PM
To: vanagon@GERRY.VANAGON.COM<mailto:vanagon@GERRY.VANAGON.COM>
Subject: Rear Heater Block-off:  Does it hurt or do any damage?

Now that I have isolated the source of the coolant inside of the van - I
have blocked the two hoses. Can I run it for while that way, until I can
get everything repaired.

Thanks,

JOhn