According to Tim Hill, the oil-pan-to-retainer stud part number is 88351-S8; however, it could not be found on Hill's Thunderbird site. I then did a web search of the part number and found it on NPD's site. The studs cost $2.06 each, but shipping will exceed the cost of the studs. Nuts & washers are not included. 

FYI: The specifications listed by Dorman for the 23733 stud kit is incorrect. One end is 5/16-18 and the other 5/16-24 (as they should be); however, Dorman says that the 5/16-18 end is 7/16 while the 5/16-24 end is 5/8; this is backwards. The 5/16-18 end is 5/8 while the pan end is 7/16. The specified OAL of 1 1/4 is correct, but the included nuts are 5/16-18; they should be 5/16-24.One other thing: Dorman's photo displays zinc-plated studs, but they are black oxide. 

I've sent an email to Dorman's Customer Service and pointed out the error. Unfortunately, retailers are using Dorman's specifications. 

Thanks, Richard. I had already ordered Dorman 23733 Water Pump Stud Kit from Walmart. The retainer cap end is 5/16-18 x 7/16 and the pan end is 5/16-24 x 5/8. OAL is 1 1/4. It hasn't arrived yet, but I guess it will do. 

Blackie,
I had ordered an assortment of  studs. 7/8 1 1/4  1 1/2. I can return the ones I don’t use.  

Blackie,
I had ordered an assortment of  studs. 7/8 1 1/4  1 1/2. I can return the ones I don’t use.  

OPPs it was 9l16 lower and 7/8 upper in length
they also have 3/4
my search was 5/16 double ended stud 

I just went to Amazon's site and searched 5/16-18 x 3/4 and found nothing that size. Is 3/4ths long enough?

Got 3/4 on Amazon

The studs are 5/16-18 on the retainer cap and 5/16-24 at the oil pan. Ted said that the overall length of the original studs is 7/8ths; however, the shortest studs I could find have an OAL of 1 1/4. 

Found em on amazon