Dual i single out system on.a 2.7
 

My 75 runs grest, sounds even better and it usese the stock exhaust with single in single out.
I have a set of 74 2 in 1 out exchangers and stock mufller.
Are they worth installing?
Will the sound be louder or quieter?
Will the hp gain be worth it?
Thanks in advance for your input.

Stock is stock so I wouldn’t think sound will change much.
Probably more power available with the 74 heat boxes.
Check your stud thread lengths as the 75 could have had thermal reactors so the stud threads would be longer
Bruce

Car was delivered to jersey. I do not think it had thermal reactors. But i will check

If it has the thermal reactors, they are worth ditching for multiple reasons, notably excessive engine heat which causes engine longevity issues.

Luckiky it does not gave thermal reactors. Has a crossover pipe, a silencer and a onevin onevout muffller,