I'm going to be converting my 4-spd. car to a 727 automatic and have a question about trans. pans. What I would like to know is whether or not it is a good investment to purchase an extra capacity deep pan for a street driven only car or is a standard factory pan sufficient? I won't be doing any racing so that is not a factor. Engine is a stock stroke 340 and the rear has 3:55 gears.

Stock pan will be fine for that application.

if it were me, i would use an A518 pan.
that one is just a touch deeper, holding maybe two quart more, is easy to find, and WAY less expensive than deep aluminum pans.
whatever you decide, install a magnet in the pan. those are more effective than the magnetic drain plugs.
just my opinion. your mileage will vary.

You won’t regret doing a deep pan

I wouldn't hesitate now to use a stock pan in your deal
I installed a tranny temperature gauge in my last street and strip pump gas car that I beat on the street and track with 10. inch high stall converter and later put a 9.0 inch T/A SS Hemi converter in the car with no other changes, the tranny temps never got above 220 F at the track when going rounds or on the street in the summer.
The motor made over 700 HP and more torque than HP, 3450 lbs. with me in it and it ran 10.00 at 134.+ MPH in the 1/4 mile
The tranny temp on the street were usually below 160 F, NOT GOOD
ATF needs to be at least 160 F or above for some of the additives in them to start working properly

I think if you go with the 518 pan you may need a filter extender plate. But I could be mistaken.

You can still run it with the stock filter. The fluid level doesn't change.

https://bestruth.top/index.php?main_page=product_info&products_id=102844. Wouldn't hurt any.

Or since the pan is off, run the later model plastic filter.

That's what I'm doing. You can pick up a Dorman 518 pan for <$50

Needs an extension to get down to the cooler fluid. Bottom of pan should catch the slip stream.

Not doubting what cab is saying, but I had a diesel I pulled with and the trans ran hot enough to go into limp mode. I put on a deep pan and that helped it. The stock pan on that E4OD was way deeper than on a 727.

It really doesn't need the extension. You can run it, but it's not like you are adding 3" of fluid under the filter. There will be basically no difference in fluid temp with that pan.

In your application as others have said the stock pan should be just fine . The factory cars went over 100K with no maintenance. If you should decide to change pans I prefer the cast aluminum as the flanges are less prone to warping

don't forget to use the new style gasket as well.
way better than cork or rubber in my opinion.
your mileage will vary.