Here is what I found, looks like you have 1 of 30 that had this mod:
50 Twin Bonanza (TC 5A4) - 6pClwM; two 260hp Lycoming GO-435; span: 45'3" length: 31'6" load: 1700# v: 202/190/64 range: 1155; ff: 11/15/49. Straight tail; ATC in 1952. Other standard motors in A- through J-50 were 275hp, 295hp, and 340hp Lycomings; some D models fitted with 400hp O-720. To USAF as L-23.
A50 1949 = Pre-production batch. POP: 11.
Beech B50 [N35738] (Flying)
B50 1953 = Increased payload and speed. POP: 99.
C50 1955 = 275hp GO-480F; v: 210. POP: 250.
D50 1956 = 6p with two 295hp GO-480-G206; span: 45'4" length: 31'7" load: 2200# v: 214/203/71 range: 1650 ceiling: 20,000'. POP: 154. Subclasses through 1961 were D50A with 285hp GO-480-Gs (POP: 44), D50B (POP: 38), D50C (POP: 64), and D50E (POP: 47).
E50 1957 = 340hp GSO-480A. POP: 70.
F50 1958 = Increased fuel capacity (230 gal); 320hp GSO-480B; length: 31'7" load: 2540# v: 240/228/80 range: 1650. POP: 25.
G50 1959 = Minor refinements; 340hp GSO-480A. POP: 24.
H50 1960 = Airstair door, redesigned wingtips. 7p with two 340hp GSO-480A; span: 45'4" length: 31'7" load: 2280# v: 235/223/83 range" 1650 ceiling: 28,000'. Junior JATO rocket system available. POP: 30.