I found this over on
www.grmotorsports.com and thought I'd keep it handy here.
This is a list of aluminized exhaust elbows you can buy at your local NAPA. There are a bunch of good numbers at local stores and warehouses.
(45* od/od)DIAMETER/A-B LENGTH/RADIUS/PART NUMBER
2.5"/6"-6"/4"/41438
2.75"/6"-6"/5"/41440
3"/4"-4"/3"/414641
3"/7"-7"/6"/41428
(45* id/od)DIAMETER/A-B LENGTH/RADIUS/PART NUMBER
2"/6"-6"/4"/41187
2.25"/6"-6"/4.5"/41188
2.5"/6"-6"/4"/41437
2.5"/6"-6"/5"/41189
2.75"/6"-6"/5"/41439
3"/7"-7"/6"/42760
(90* od/od)DIAMETER/A-B LENGTH/RADIUS/PART NUMBER
2"/9"-9"/4.5"/41631
2.25"/12"-12"/4.5"/41762
2.5"/12"-12"/5"/41432
3"/3"-3"/3"/41221
3"/6"-6"/3"/41685
3"/7"-7"/3"/41536
3"/10"-10"/6"/41434
3"/14"-14"/8"/42344
(90* id/od)DIAMETER/A-B LENGTH/RADIUS/PART NUMBER
1.5"/6.375"-6.375"/4"/41231
1.75"/6.375"-6.375"/4"/41000
1.875/6.375"-6.375"/4"/41230
2"/6.375"-6.375"/4"/41001
2"/7.875"-6.375"/4"/41154
2"/9"-9"/4.5"/41558
2.25"/6"-6"/4"/41098
2.5"/6.25-6.25"/4"/41002
2.5"/12"-12"/5"/41441
2.34"/6.375"-6.375"/5"/41099
2.34"/12"-12"/5"/41442
3"/8"-8"/6"/41365
3"/10"-12"/5"/41535
3"/12"-12"/5"/41534
3"/14"-14"/8"/42759
3"/14"-14"/6"/42445