The two most common transmissions to consider for the V8 Volvo are shown above: The 700-R4 (or 4L60) automatic overdrive transmission is shown on the left, and the Borg-Warner T5 5-speed manual transmission is shown on the right.
The purpose of showing these transmissions is so you understand the size difference between the manual transmission and the automatic transmission. They are both the same length, but the widths and profiles are different. The manual transmission can be installed with minimal transmission tunnel modifications, but the automatic transmission requires substantial metal movement (hammering) on the transmission tunnel, and some cutting.
Most of the hammering required for the automatic transmission installation is to make room for the transmission dipstick tube (not shown), the servo housing (arrow), and the transmission oil cooler lines (not shown). Also, hammering is required to make room for the shift linkage.