BTR21399 Flexplate Adapter Kit for GM LS Engines to GM TH400/TH350/700R/Powerglide Transmissions

Name: BTR21399 Flexplate Adapter Kit for GM LS Engines to GM TH400/TH350/700R/Powerglide Transmissions
Brand: BRIAN TOOLEY RACING BTR
SKU: 559-BTR21399
Price: 229.99 USD
Availability: InStock

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Flexplate Adapter Kit

GM LS Engines

Fits GM TH400, TH350, 700R, and Powerglide Transmissions

High-Strength Steel Construction

Includes Adapter, Flexplate, and Hardware

The BTR21399 flexplate adapter kit allows GM LS engines to mate with GM TH400, TH350, 700R, and Powerglide transmissions using a standard length pilot and 11.5 in. converter bolt circle. The matched components provide a reliable interface for high-performance drivetrain combinations.

Brian Tooley Racing BTR21399 Includes:

Adapter Plate 12563532
Flexplate 19260102
Six Bolts BTR57940

Brian Tooley Racing BTR21399 Features:

Enables GM LS engine installation with GM TH400, TH350, 700R, and Powerglide transmissions
Uses standard length converter pilot and 11.5 in. bolt circle
High-strength components suitable for performance applications

Flexplate Adapter Kit for GM LS Engines – Smooth Transmission Swaps

If you’re installing a TH350, TH400, Powerglide, or 700R4 transmission behind a GM LS-series engine, the Brian Tooley Racing (BTR) Flexplate Adapter Kit makes it a clean and reliable bolt-on solution. This adapter kit avoids the need for major transmission tunneling or machining and works exclusively with torque converters having a standard pilot length and 11.5 in. bolt pattern—common on TH350, TH400, Powerglide, and 700R4 applications. A spacer, flexplate, and hardware are included for a straightforward drop-in installation.

Part TypeAutomatic Transmission Flexplate

Product LineBrian Tooley Racing BTR Flexplate Adapter Kit for GM LS

BrandBRIAN TOOLEY RACING BTR

Package Height2.8

Package Width14.7

Package Length14.8

Weight7.25 PG

Part CategoryPerformance Parts

Ring Gear Tooth Quantity168-Tooth

QuantitySold as a Kit

Part FitmentDirect Fit

Engine Make/SizeGM Gen III/IV LS