You didn't say if your 1.5 ton is Chevy, or GMC. GMC radiators mount on the FRONT of the radiator support-that would give y ou some add'l length. There is a gentleman(name slips me right now) on the inliners board who makes adapter plates for CBOP which should work for you. GMC 302's can be bored out considerably(close to the 320 of the Buick) which would make an easier fit, unless you are in love w/ straight 8's. You might want to look for a 5 speed rather than a 420, even an OD if you are lucky.

Last edited by EdPruss; 02/15/2012 6:18 PM.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.