I think you can do it, but why? You'll need all of a Toploader except the case, can't see it being any cheaper. The external linkage OD is a good trans, I had one on a 351W for 100K miles with no problems. The shift gap is a bit wide, but an engine with torque overcomes that.Your 3.00 gears are admittedly too tall for OD, though, unless you have a strong 390 or something like that. I sold my spare OD to a guy who put it in a '68 428 Galaxy and loved it, don't know what his gears were. I know he didn't change them, though.