missshifting a 67

hey all.
my buddy and me are redoin his 67 and it is clean as all right now new radio and all but anyway.
the motor was put in new sometime ago from his dad. also replaced the shift coupler. but no matter how hard we try we cant find 1st and 2nd when we are driving around the streets.
it feels like its going but has alot of play and is loud ratteling type sound into 1st and 2nd. 3rd and 4th are all good.
any ideas on how to get this chekced out (like a checklist or something)
his dad wont fund a new tranny and we are broke so is there a way to just run throught the possiblilities

thanks

You can try unhooking the shift linkage under the rear seat & see if you can put it in 1st & 2nd then. If it goes in then the shift lever linkage is out of adjustment.