88-98 Chevy GMC OBS & C1500 Bolt-In Rear Frame C-Notch Kit

88-98 Frame C-Notch Kit - #135-4005

Modernize your 1988-1998 Chevy & GMC C1500 (OBS) with the most robust bolt-on C-notch kit on the market. Engineered with the builder in mind, this kit provides the necessary axle clearance for lowered stances while significantly reinforcing the factory frame rails. Precision-manufactured for the GMT400 platform, this kit ensures a professional-grade foundation for trucks lowered more than 4 inches, preventing harsh axle-to-frame contact without the need for a welder.

The GSI Advantage

• 100% Bolt-In Solution: Designed for ease of installation, this kit eliminates the need for extensive fabrication. It’s a straightforward process that can be completed with basic shop tools, making it the ideal choice for a one-person install.

• Maximum Reinforcement: Measuring an impressive 25.5" in length, our notches distribute stress loads across a much larger surface area than standard kits. This added length significantly increases frame rigidity and strength.

• Premium Corrosion Resistance: To guarantee long-term durability and a show-quality look, every notch comes finished in a semi-gloss black powder coat.

• Precision Metal Template: We include a heavy-duty metal installation template to ensure perfect alignment and cutting. This removes the guesswork, ensuring your notches are positioned exactly where they need to be for maximum travel.

Design & Construction

• Weight: 42 lbs (Total Kit) / 21 lbs (Per Notch)

• Dimensions: 25.5" x 3.5" x 5.25" (Per Notch)

• 1/4" ASTM A1011 Hot-Rolled Steel: Laser-cut and precision-formed for a strong, accurate fit over the factory GMT400 frame rails.

• Overbuilt Hardware: Includes (32) 1/2"-13 Grade-8 hex bolts for a secure, permanent, and vibration-free fit.

• Finish: Semi-gloss black powder coat.

Measurement & Fitment Guide

This kit is engineered specifically for the 88-98 C1500 (GMT400) frame. Proper fitment is critical for maintaining suspension geometry and safety.

When to use this kit:

• Rear Drops: Required for rear drops of 4" or greater to maintain proper suspension travel.

• OBS Builders: Specifically contoured for the 1988-1998 Chevy/GMC C1500 frame rails.

• High-Performance Use: The 25.5" extended design makes this ideal for high-horsepower or heavy-use street trucks that require extra frame support.

Vehicle Applications

• 1988-1998 Chevy C1500 (2WD)

• 1988-1998 GMC C1500 (2WD)

• Fits "OBS" / GMT400 Platform Regular Cab, Extended Cab, and Crew Cab models.

What’s Included

• (2) Driver & Passenger Side C-Notches (25-1/2" Long)

• (1) Precision Metal Template

• (32) 1/2-13 Grade-8 Hex Bolts

• (32) 1/2-13 Grade-8 Lock Nuts

• (64) Grade-8 Flat Washers

Questions? Contact Us

(480) 940 1806 – Local
1 (877) 951-1890 – Toll Free