There are four steps in researching
Find the year and Public Law [ P.L.] number of the statute in Purdon's Pennsylvania Statutes (in print at KFP30 1973 .A44; also available on Westlaw).
Check the Historical and Statutory Notes in Purdon's under the provision you want to research. Note the year and P.L. number, i.e., the pamphlet law page number on which your act begins, not the act number.
Find the bill number in the Laws of Pennsylvania (KFP 25 .A23). This set is the annual compilation of session laws, or state acts arranged in chronological order by date of passage. The P.L. number corresponds to the number of the page on which the law was published. Near the top of that page, look for the bill number (preceded by either SB or HB) and make a note of the bill number and the year.
For older legislation, find the entry in the History of House Bills (KFP 15 .P42) or History of Senate Bills (KFP 15 .P43). Find the volume for the year of your bill. All volumes are shelved together under the same call number. The entry will give you potentially important dates in the history of the bill's progress through the legislature. There may also be a reference to remarks published in the Legislative Journal for one or both chambers.
For more recent legislation, you can search the Pennsylvania General Assembly website by bill number, as well as by subject matter or sponsor name. The General Assembly provides only bill text and short title information for legislation from the 1953-1954 session through 1969, and search options may be limited. Amendment information is available for bills from 2007 to the present.
Find the debates in the Legislative Journal. If any remarks were published, note the date, the chamber, and the page numbers. You will find them in the Legislative Journal for the House of Representatives (Folio KFP 18 .P42) or the Senate (Folio KFP 18 .P43) in the third floor Folio (oversized) section.