Winter Aircraft Scheduled for BOS/IAD ?

Anbody got any ideas on which aircraft will be servicing BOS/IAD over the Winter period?
I have a companion voucher to burn so was thinking of a weekend at either of these places in March, but the trip would be in PE, so i would want to be on a 744 or 346 rather than the 343 - and dont try and persuade me to upgrade to UCS - my credit card cant take it!!!
:D
I know that aircraft can change last minute, but it would be handy to know whether either of these routes are 744/346 equipped this season.
I have a companion voucher to burn so was thinking of a weekend at either of these places in March, but the trip would be in PE, so i would want to be on a 744 or 346 rather than the 343 - and dont try and persuade me to upgrade to UCS - my credit card cant take it!!!

I know that aircraft can change last minute, but it would be handy to know whether either of these routes are 744/346 equipped this season.