I see in the Jegs catalogue that they have the 520-16820 for an '83-'92 305, and below it there is a 520-16822 for an '83-'85 305 H.O... What is the difference between the two? Thanks for any replies, I know it is a dumb question but I would rather be safe than sorry.

 

If your 84 has the oval 4 bolt cat you need 16822. The other part is for the wimpy 2-1/4 inch flange cat on lo po 305's.

 

And should you need a high-flow cat, here's a bolt-up from Summit:

Catco 4116

JamesC

 

Okay thanks. So basically you can tell (if it's the original) whether a car is an LG4 or an L69 just by the cat? I haven't gotten around to looking at mine to find out what engine is in it even... It's at the mechanics I do remember however, that the cat was oval-ish and I'm not even sure if it's the original, but I would assume it is. Looked pretty new, but didn't have any company stamps.

 

Possibly, but the L69 Y is a better indicator (vs the LG4):

https://www.thirdgen.org/forums/exha...aust-pics.html

Here's the cat:

https://www.thirdgen.org/forums/atta...y-pipe-cat.jpg

JamesC