Engine Swapping EFI distributor for carb distributor- shaft length is different

I have an 88 GT that was carb swapped prior to me buying it. I installed a gt40p motor from an Explorer. I have been running the new engine on the previous carb and distributor setup.

I bought a replacement distributor for an 85 5.0 Mustang since I want vacuum and centrifugal advance. I was getting ready to install the replacement distributor and noticed that the shaft length is different- see picture. The length of the original shaft is about 1/2 inch longer than the replacement that I bought. I checked the depth of both shafts where the oil pump drive shaft goes in and the original shaft is about 3/8 of an inch deeper. Did I get the wrong distributor or is this a normal difference between an EFI and carb distributor? Will the replacement distributor go down far enough over the oil pump drive shaft?

Also, I read somewhere that on these aftermarket distributors, the gear was installed at the improper height. I used a tape measure and checked the distance from the flange that meets the engine block to the top of the distributor gear and it is pretty close between the EFI distributor and the replacement distributor. The gear is about 1/16 to 1/32 farther up the shaft on the new distributor. Is this anything to worry about?

Okay, thanks for the reply and information!

I was starting to get paranoid that the oil pump driveshaft length changed somewhere along the line and the new distributor wouldn't engage the oil pump. Thanks for clearing that up for me.