I have an 87 GT and am building a 351C for install through winter right now it is a 5 speed and am going to switch to auto i would like to use C6 but dont know about clearances or do I have to use a C4 Thanks for your help

 

c6 will not fit without some cutting. built c4 will be fine my friend has one behind a 900 hp nitrous sbf.

 

A little off topic, but what is the letter code for the 5 speed tranny? i have an 86