Guidance is give in FAA Document 8900. If you have a Commercial certificate with a type rating in a multi-engine land aircraft (in your case the B737), once you take an ATP checkride in a multi-engine aircraft your type rating is elevated to that of ATP standards. You do not have to redo your type rating. See excerpt below:
Type Ratings. Type rating tests are conducted to the ATP standard for all grades of pilot certificate. Therefore, all type ratings in that category and class of aircraft for which the practical test is conducted in are upgraded after successful completion of the practical test. For example, a person who holds a B-737, DC-3, and SK-62 at the commercial pilot certificate level, and later satisfactorily completes an ATP practical test in a CE-750, would have his/her B-737 and DC-3 type ratings elevated up to the ATP certificate level. The SK-62 would not elevate up because the practical test was in a multiengine airplane. However, when the person satisfactorily completes an ATP practical test in a helicopter, the SK-62 would then elevate up to the ATP certificate level. Therefore, all of the type ratings held on the superseded certificate carry forward at the new certificate level within category and class.
NOTE: A type rating for a single-engine airplane may not be upgraded to the ATP level.
1) Except for type ratings and, under some circumstances, the instrument rating, other ratings indicated on the superseded pilot certificate are carried forward at the commercial, private, or recreational level, as indicated on the superseded certificate.
2) Instrument rating privileges are shown on the ATP certificate only if the ATP practical test was for visual flight rules (VFR) only, or to retain instrument privileges that were held on the superseded certificate for a category of aircraft other than the one used for the ATP practical test.