The Protect-o-Plate relies upon the application code stamped on the motor's identification pad for warranty information. Same for the tranny. It could have been a base 190 hose 283 or a base 275 horse 327 in '65 if the trim tag says V-8. It could also have been the ultra rare 409 425 horsepower 409 if the car's build date was before Feb, 17, 1965. As stated the only way you know for certain that you had a four speed Muncie and not the possibility of a three speed would be if you had a 350 horse 327 or a big block under the hood (All three of those motor choices required a Muncie if you ordered a manual trans). The Protect-o-Plate will list every other option that was installed on the car at the time.
The SS could be had in 1965 with a 153 cid four cylinder if you insisted hard enough and paid up front for such a whimpy car. Or it could have come with a 230 or a 250 cid six cylinder, a 283 cid V-8, a 327 cid V-8, and either a 409 or a 396 V-8 depending in which half of the production year you bought the car. This was because a SS doesn't get you any performance equipment at all in 1965, it was strictly a trim level of badges and chrome.
The only way to buy a factory built hot rod in 1965 was to buy a used police car, but police cars were all stripped down Biscyanes with rubber floor mats (for when your drunk in the back seat lost his three Martini lunch). A RPO code of 9C1 police car came equipped with HD suspension, HD battery and alternator, HD cooling with an oil cooler added to a larger radiator, and an automatic tranny (or PowerGlide in 1965).
Not all police cars however came with cop motors despite what Elwood told Jake in the movie. Most departments wanted fuel economy because the cars where never turned off once cranked up. They ran or idled continuously so most cop cars had the two barreled 283 motor. The exception to the no big engine in a cop car was of course a highway patrol cruiser; which was tasked with running down what ever offending vehicle that it encountered. A Highway patrol cruiser would have had the 350 horse 327 or a 409/396 in 1965.
If you want a high performance ride and an unusual car to show on weekends build a black and white patrol car. Thought the twin lamp or four lamp beam red Fedral Signal rotating roof light might be hard to find. Back in 1965 they were using a round dome model 175 or a model 15 light for the smaller twin beam mounted on each side of the roof.
Here is a picture of a 1965 Impala Police car
Here are Two 1966 police cars in pursuit with lights flashing
The other two are Fords