Not all turbos can be made into dual bb. It all depends on the wheels.
However, you can get a TE44 with the dual bb chra from PTE. It's called a TE-4431RE. Might want to check with them for availability. Same compressor wheel and turbine wheel, just has the Garrett dual bb cartridge. Pete, Joe or Brian can hook you up over there. Although it is not listed on their website, it was a turbo that I sold before, not only to Buick customers, but also to Sport Compact customers as well. Here's a generalized quick list of them from PTE you can get with Buick 3-bolt housings, 3231RE, 3431RE, 4431RE, 6031RE, 6031RS, 6131RE, 6131RS, 6131RSP, 6176RE, 6176RS, 6176RSP, 6776RS, 6776RSP, 6776RH, and lastly 6776RHP. The 3231RE and the 3431RE are not normally known as Buick specific turbos, but more along the lines of Sport Compact turbos. The 44, 60, 61 & 67 are more well known as Buick turbos, some vendors like to give them their own part numbers, which can be confusing. The 6031RE is what is known to the Buick world as a TE60 with the ball bearing cartridge. 6131RE thru 6176RSP is the PT61 with either the stage 3 T31 turbine wheel, or the 76 P-trim wheel and the ball bearing cartridge. The 6776RS thru 6776RH is the PT67 with a P trim turbine wheel, bb cartridge and whatever compressor cover you want.
HTH
Patrick