Hi ! I guess this will not turn out "cheap" anyway. The 250 will not fit your orig. bellhousing, and the new trans. will not fit your closed driveline (1/2ton truck), so you will need a new rearend and driveshaft too, in addition to new engine and trans. mounts. And your orig. clutch and brake pedals will not fit the newer eng/trans, so you need to fabricate mounts for them too.
A 270/302 will fit your orig. bellhousing/trans. and front eng. mount. So you must be realistic and calculate all costs involved for both alternatives, to see if any of them are "cheap", even if your 250 is for free.
