Intake plenum

[iron butt]

I'm changing the motor in my 90 BII which according to the date stamped on the old block is 6/87 - 20C. The motor I'm installing has 11/89 - 20F and is out of an 89. I noticed that the plenums are a little different as one is slightly longer than the other in the snout to the the throttle body. I can't remember which plenum was on which motor and wondering if it makes any difference which one I use? The numbers on the plenums are RF-E67E-9425-CB (cast) / P2 04217ML (stamped). The other one is RF-E87E9425-AA (cast) / 06B2289 (stamped). The Bronco has cruise control with an automatic transmission.
The other question is the ECM, I have the one from the 89 and it was a manual transmission. The one in it with the old motor was already is for an automatic transmission. I'm not sure if the ECM was swapped for the 87 and does it make a difference? I'm assuming that the ECM is the original with the 90 motor, but yall know about assumptions, and they usually bite me in the ass.
The original motor was swapped a long time before I got it.
Thanks and I'll probablly have more questions later.

 

[RonD]

1990 should be a speed density system so no MAF sensor, it used MAP sensor, so either air plenum can be used.
I think Calif. 2.9ls had MAF sensors, so air plenum was more important.

The A4LD trans needed the EEC(computer), so that should be the one you use.

 

[adsm08]

And you have to watch which setup you end up with in the end. 87 had things like EGR and a knock sensor that were deleted in 88 and never brought back. If the 87 computer is the auto trans one and you want to keep the auto then you will need to get the other control devices installed or you will have a CEL and it may not run right.

 

[iron butt]

Thanks for the info. Right now it's to freakin' cold to mess with it.