TNT in vitro transcription/translation system

[Frank O. Fackelmayer]

Hi all,
We sometimes use in vitro translation to get protein synthesized from cDNA
clones. In the last time, we´ve used the Promega TNT system for coupled in
vitro  transcription/translation, which works very well. We have been
using the T7-polymerase based system, and now I need a T3-polymerase
system for only one or two reactions. I got plenty of the T7 system left,
and I thought that adding T3 polymerase instead of the T7 polymerase
should do the job (reaction conditions for the two polymerases are
essentially the same in standard in vitro transcription assays). Has
anybody tried that? Successfully? How many units of polymerase do you use?
I really dont want to buy a complete T3 system for only one or two reactions.

Thanks,
Frank