ohhh more questions
No DG head made for 400. possibly could get special ordered ones for 250's??. ive seen one on RM 250 T. havent seen any in DG catalogues but that doesnt mean they were not made as ive seen DG ads for head for CR 480, YZ 490 and RM 500 but they are not listed in DG catalogues. i have one for the 250 though
best chance for aftermarket head for PE 400 would be to find one off a big bore bike with same stud pattern and then modify/improve dome to suit. you might be able to find a Webco or FMF head, they made some heads for big bore bikes.
the shocks on DG PE were aftermarket KYB air shock. possibly you could have got Works Performance too but i think the KYB air shox is what they mainly sold. they were annodized gold. they are OK but not as good as dual air chamber fox airshoxs. i have plenty of fox airs and ohlins for my bikes.