I've restored a few Advance Design beds in the past so I know some of the surprises that await the first time restorer.  I'll try to help alleviate some of those surprises by including as much information as possible on what I know about the different bed varieties, board widths, board thickness, components, parts suppliers and restoration methods.

BED VARIETIES:

Chevrolet and GMC 1/2 ton beds starting in 1947-'53 had the following dimension:

• Depth x Width x Length = 15" x 50" x 77"

• Depth x Width x Length = 15" x 50" x 85 3/4"

• Depth x Width x Length = 17" x 50" x 77 1/4" for the 1/2 ton
• Depth x Width x Length = 17" x 50" x  89" for the 3/4 ton

GMC'S LONG 1/2 TON

• GMC Corporation had all the similar bed configuration as Chevrolet but due to it's stronger engines with full flow oiling, it was able to offer the long 1/2 ton truck as an option to its buyers well before 1954.  The long 1/2 ton incorporated an extended frame to support the lengthened box on the 1/2 ton chassis.   This lengthened box was only available on the Chevrolet 3/4 ton chassis.   The long 1/2 ton can be distinguished from the 3/4 ton by the quantity of lug nut on the rear end.  If the rear end has 6 lugs then its a long 1/2 ton but if it has 8 lugs then its a 3/4 ton.

BOARD WIDTHS:

The boards width depended on what position they were placed on the bed end cross sills. You can kind of get an idea of the bed wood width and for that matter a clue to the beds year "if the bed happened to have been changed at one time" by counting the wear strips in the bed or if their missing the holes for the wear strips in the front or rear cross sills.   If their are 8 holes in the sill then the bed is from a 1947- Early 1951 series.  If their are only 7 holes in the sill then the bed is from the Late 1951-54 series.

The tables below show the width of each board and its relative position.
 

WOOD THICKNESS:

BED WOOD SPECIAL MILLING FEATURES:

The edges of each board  "except the outer most edges of the two outer bed boards" are milled with a special groove which allowed the:

• board to expand and contract due to climate changes without bending or cracking.
• metal wear strips to ride on the wood and be slightly higher then the wood to reduce the likely hood of material coming in direct contact with the wood and increasing wear.

BED CROSS SILLS:

The number of bed cross sills depends on the year of the truck and it's model.

 

CHEVROLET  & GMC BED'S 
CROSS SILL'S

	Chevy/GMC 1/2 Ton Bed Length	GMC Long 1/2 Ton Length	Chevy/GMC 3/4 ton Bed Length
1947-1948	5	5	5
1949-55 1 St. Series	4	5	5
1950	4	5	5
1951	4	5	5
1952	4	5	5
1953	4	5	5
1954	4	5	5

 

 The 1/2 Ton Beds from 1947-48 have five bed cross sills:

•  one attached to the front bed panel
•  two just before the frame kick up
•  one behind the frame kick up
•  one at the rear which contains the pads to bolt the bed to the frame and hold the rear of the bed together.

The 1/2 Ton Beds from 1949-54 1 St. Series has four bed cross sills:

•  one attached to the front bed panel
•  one just before the frame kick up
•  one behind the frame kick up
•  one at the rear which contains the pads to bolt the bed to the frame and hold the rear of the bed together.

• one attached to the front bed panel
•  one just before the frame kick up
•  two behind the frame kick up
•  one at the rear which contains the pads to bolt the bed to the frame and hold the rear of the bed together.

BED INSTALLATION AND WOOD SPACER BLOCKS:

FIRST CROSS SILL:

Probably the easiest of all the cross sills to install because it's bolted to the front bed panel.  This cross sill is also drilled for the front bed to frame mounting bolts to pass through.  This cross sill requires a 2" wood spacer and a 12 inch long 3/8 carriage bolt to pass all the way through the frame and tighten to the lower edge of the frame.  The 1947-53 requires the 12" bolt while the 1954-55 1st Series only requires the 6" bolt.

SECOND CROSS SILL:

This cross sill only bolts to the lower side of the wood and not the frame.  The cross sill adds support to the wood to avoid cupping.  It's bolted just in front of the frame kick up and when installed will be just above the frame by 1/2" or so and only contacts the frame when a heavy load is encountered.

THIRD CROSS SILL:

This cross sill installs like #1 described above with a 2" wooden block and secured with a carriage bolt which ends just below the top frame edge.  This sill is located just behind the frame kick up and it's placement can be easily determined by locating the frame hole behind the kick up which is where the carriage hold down bolt will pass through.

FORTH CROSS SILL:

This cross sill is basically the back section of the bed that holds the sides together.  The rear sill has a metal pad welded to the cross sill so no wooden block is required to level the bed, only a rubber vibration pad to eliminate squeaks.
 

SPECIAL NOTES:

•  All bolts that secure the bed to the frame will require the special shaped bed washer to keep the bolt from turning when tightening.

• The bed washer is countersunk into the wood for a flush fit.

• The 1954 cross sills are taller then the 1947-53 cross sills due to the change in frame design and the elimination of the bed wood spacers.

MATERIAL SUPPLIERS: