Question when ordering PSI Harness (LQ4)

[brady01]

Trying to order my PSI Harness for my 87 r10. I've got a 2005 LQ4 / 4L80 out of a 2500 Express Van. When I try to order it asks what MAF Sensor I have, however I don't have one at all so I'm going to have to order one. What style do I need to look for ?

And also how do I know what Injectors my engine has? It also asks that. Whatever comes in an LQ4 stock is what I have but how do I know what that is ?

I also need an alternator. So do I just order an alternator for a 250p express van and then order my harness accordingly? If so do I want 105amp or 145?

Sorry for all the questions, this is all making my head spin.

Thanks in advance!