I put in the John Craig TE44 (more or less the same unit ) and a 3200 stall converter from Bruce (9/11 on his website) and between the two, the car has responded very well. Both the turbo and the converter were stock units.
You will need plenty of fuel to take advantage of the bigger unit, so do not skip that upgrade if you haven't already done so.
Pete, below 18#, you will probably not notice any improvement. As you increase the boost, the stock turbo becomes inefficient and begins to heat the air charge excessively. The 49 picks up where the stock quits and remains in its efficiency zone to at least 26#.
A stock turbo/injectors will take you to low 12s and some have gone high 11s. A 49 with appropriate matching injectors can take you to near the mid 11s IF everything is mechanically sound in your engine and you have the matching componets required to support the hp.
A stock converter should work fine with the 49 or the 44.