I see that your trans is the short tail shaft did you compare with the trans you toke out to make sure it the same length. Because then you might need a new drive shaft . Most trucks have the 6" tail shaft on them. But depeneds on the trans you toke out.
77 1/2 ton Heavy Half chev 454,350TH,3.07rear driven 6 YR now changed back to 85 monte carlo SS 305 Motor as of 2004, june,30 inter changed to 84 GMC style, flatbed with a 98 van bumper.