This page is left for tech info on the 401/425 nailhead and the 65/66 Skylarks. Since I have no practical driving time on my rig, I appeal to you for information to share with others. This information has just been compiled from conversations and the collection of literature out there. If you have anything to add, please use the link way at the bottom of this page. Thanks!
The best dual quad manifold for the nailhead is the aluminum Edelbrock B262.
Edelbrock Performer has an 850 cfm on the market.
Need a quadrajet gasket for your nailhead utilizing the exhaust crossover runner? - use MOPAR part #4306309.
You can stroke a 401/425 nailhead by using 364 rods.
Crower can stroke your nailhead - about $2.5k for the crank, $1.1k for the rods, $1k for pistons/pins/rings. 5 months build time.
455 rod bolts fit the nailhead so ARP bolts will work.
455 harmonic balancers will work with the nailhead. ATI (PN#918400) and BHJ are some aftermarket suppliers. Modifications are required (BHJ at least - not sure about ATI).
Damper Dudes rebuilds stock nailhead balancers to better than stock - 1-800-413-2673
TA Performance offers a steel billet flywheel at stock weight. Three clutch patterns drilled #TA2037
Line up dimple on crank flange to alignment hole on flywheel/flexplate for correct installation.
Valve Train + Cam
Weber used to make a solid cam, the "F-6".
Adjustable Rockers used to be made by Gotha.
Roller Rocker Arms are in the works for the nailhead!
You can still get cams ground by Comp Cams.
Chrysler makes an offset keyway set that fits the nailhead cam gear (fits the sb Chrysler # is p4286500 avail from PAW or Mr. Gasket)
Adjustable pushrods from Smith Brothers.
ARP has main bolts along with head studs available in kits- ensure to get 1/2" longer studs for the alt bracket.
Totally Stainless has a stainless bolt kit for the nailhead.
Mallory has a billet Unilite non-vacuum advance distributor - # 372920001 - With vacuum advance #472920001 - Recurve Kit for both #29014.
A new low weight starter has been introduced by Thomas Telesco.
Gaskets N' Such
Buick 400-455 neoprene front seals will fit the nailhead (National #450446).
2" grommets on valve covers - PN#02946079 from a 360 Dodge truck valve cover.
Flowkooler has a water pump for the nailhead along with Robert Shaw thermostats.
Be Cool is releasing a crossflow alum custom rad for the 65-67 Skylarks early 01'.
Sanderson and Rodworks has block hugger headers for the nailhead.
The Buick Gran Sport Club of America occasionally has runs of the Hooker style headers for the 65/66 GS Skylarks.
Contact Bill Badd if you're interested in a set of 63 - 65 Riv headers. He'll fill you in on the details.
"No drill" driveshaft loop that attaches to tranny mount from Indian Adventures for both auto's and sticks.
Nailhead remote oil filter assembly - NAPA PN#4734 - Mr. Gasket too.
255 60/15's fit on the rear of 66's with rolling the lip and using a 4 1/2" backspacing on a 15x8 rim. (4 3/4" backspacing would be ideal).
275 60/15's will fit on 15x8 rim with 5" back space for the 65's. 8" x 28" Mickey Thompson ET's will fit on same wheels for the 65's as well.
If lower steering column bearing goes out, remove white plastic holder and install BCA #r-16-ss due to the lack of "correct" bearings. If upper control arm pressed bushings go out, replace with 67-72 A body arms.