I have a '68 C-10 with 250 and 3 speed. From what I've heard/read the T-5 will require a good bit of work. Most of the 4 speeds shouldn't be a problem. I have a M-21 but the first gear isn't low enough to work well on my truck. You'd really want something with overdrive too if you could get it. I've heard good things about the Super T-10s. I'm afraid I can't offer you much more than that. I hope this helps.
BIGGY--What rear gears does your '65 have? My truck has 3.73s and I've run my 250 up to around 75mph. Just curious.
1968 Chevy C-10, 250 and 3 speed on floor, Hedman headers, Offy intake, Edelbrock 600cfm 4 barrel, HEI
1966 Chevy C-10, motor and tranny went into the '68. Waiting to be restored.
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