Another interesting variant at Gal 1.4a: τοῦ δόντος ἑαυτὸν ὑπὲρ τῶν ἁμαρτιῶν ἡμῶν ...
As noted in NA27 P46 and Sinaiticus (among other important witnesses: A DFG PSI 1739 1881 Maj) read PERI. See the following pictures:
Sinaiticus is corrected from PERI to UPER, showing the spatial similarity of the words (ca corrector acc Sin Proj. Website; not first corrector as NA27 represents).
This is a common variation (not only in NT manuscripts, cf. DBAG), and there doesn't seem much of a differential in meaning in this sort of context. The parallel in 1 Cor 15.3 (Χριστὸς ἀπέθανεν ὑπὲρ τῶν ἁμαρτιῶν ἡμῶν ...) is obviously relevant in terms of appeal to Pauline style. But I don't have a strong feeling either way on this one. Any thoughts?