Ford Motorcraft 1G type Externally Regulated Small Case vs. 1G Large Case Alternator
You Can See The Difference!
Small Case, Left. Large Case 1G, Right Small Case, Left. Large Case 1G, Right 
For maximum low speed output the best solution is to use a larger size alternator like the example shown above which shows the difference between the small case 1G and the large case 1G. Both are 1G series alternators but, the only components that are interchangeable between the two are the pulley, bearings and a few nuts & screws. In almost all cases, the large case alternator will bolt exactly in place of the small case without bracket modification. You can also use the same voltage regulator from your small case alternator to control the large case unit. The only change, is that the large case alternator requires the use of a plug connection, shown below, for the field and stator leads to the alternator.
Purchase the Large Case Alternator Upgrade Below
$149.95 F1-1GLC-100 ....New, Ford Motorcraft type 100 amp 1G Large Case Alternator,
For External Regulator
$199.95 F1-1GLC-150 ....New, Ford Motorcraft type 150 amp 1G Large Case Alternator,
For External Regulator
$259.95 F1-1GLC-200 ....New, Ford Motorcraft type 200 amp 1G Large Case Alternator,
For External Regulator
