olds swap problems

[shin]

hi new to the forums... seems to pretty nice and busy traffic around here... but anyways... i got a 85 c10 short box, has a 350 700r4 in it as of right now... and i have been working on a 66 olds 425 from a tornado for awhile as plans to put it in my truck.. i know you have to get motor mounts from the 78-81 chevy diesel trucks and i got the motor mounts that go on the motor... but i am having problems getting the right motor mounts that bolt to the frame. i went to every auto part store around hear except napa and they all give me ones that are to wide... they are like four inches wide and the the bracket on the motor is like 2 3/4 inches wide... the wide one are for a small block... am i missing something thanks... need help soon since i want to start the swap this week and i have had the torque bug itching me for awhile. thanks for the much needed help and yes i have the right transmission i am running a dual bolt pattern built th350