It has been awhile since I looked into this, but since I (and my spouse) have SS covered earnings as well as non SS pensions, I have an interest. Here is a summary, to the best of my recollection, but I suggest you run the numbers for your situation.
The 403b does not influence WEP/GPO. This is a savings plan that is above/beyond the pension.
The person who earned the two benefits has their SS benefit reduced by WEP, subject to limits (maximum amount and 20-30 years of substantial earnings). The largest reduction is currently around $375, IIRC, but is determined based on when you hit 62.
If you are the spouse of this person and do not have any sort of non SS pension, you are eligible for spousal/widow benefits based on the non WEP reduced SS amount.
As a person who is eligible for a non SS covered pension, your SS benefit as a spouse/widow will be reduced. This is the GPO. The amount of this SS benefit reduction is 2/3 of your pension, up to 100% of the SS benefit.
Only the person who earned the non SS pension is subject to any reduction, WEP for their own, GPO as a spouse/widow. In all cases, first there is a calculation of the "normal" SS benefit based on earnings, age, etc. Then they apply the appropriate reduction.
LRDave - assuming you have all SS covered employment, DW's benefit is reduced by WEP, while any benefit she may be eligible for based on your earnings as a spouse/widow will consider GPO. There is no effect on your benefit.
It may help you think about it if you consider that WEP is directed at the dual earner, while GPO is not. A stay at home spouse who never earned any SS benefit can be eligible for a spouse/widow benefit. But if that spouse had a full career in a non SS covered position, they would be eligible for the same benefit if GPO was not introduced. That is what GPO is intended to address, IMHO.
Hopefully clearer, but hey, it is the government...