Sure, all that stuff fits. 
And 'it depends' and there are various small differences, but basically it
all will swap over.
As the one member mentioned...........the sliding door will not.

There are no 1981 stock diesel vanagons. 
Perhaps someone made an 81 air-cooled vanagon into a diesel. 

Just about everything can be installed on the older body.
The body dimensions don't really change at all in all vanagons. 

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Crawford, Neil
Sent: Wednesday, February 20, 2008 7:44 AM
To: vanagon@GERRY.VANAGON.COM
Subject: '90 & '81 Vanagon Parts

I've got an '81 Diesel, Manual, Westy and a an opportunity for a '90, Gas,
Auto, Vanagon.  Am wondering if anyone knows if any of the following with
'fit' the '81 without major modifications:

Seats (any, all)
Bumpers
Dash
Grill (either)
Carpet
Interior Panels

I'm about to take measurements in both but know there are several dimensions
(size, shape, fittings, loads, et cetera) that I'll never be able to nail
down before I buy the '90 and if anyone knows, from experience, that one of
these parts above (or any for that matter) will or will not work, I'd
appreciate it.

Neil