All kits made from High-Quality USA Aluminum and Steel. Proudly manufactured in the U.S.A.!
The FO2501 adapter kit bolts a Ford Modular V8 automatic transmission — 6R80 or 4R70W to a Ford 429/460 big block, with no grinding of any kind required on the starter, engine block, or transmission case.
Release expected 8/17/2026. Call (763) 767-4480 for more information.
Features and Benefits
- Direct Ford 429/460 big block to Modular V8 automatic compatibility — bolts on with minimal tools
- No grinding required — no cutting or grinding on the starter, engine block, transmission case, or any bolt hole component
- No more heavy torque converter spacer — the redesigned kit uses a crankshaft spacer instead, cutting weight without giving up alignment
- Serviceable starter — the starter can be replaced without removing the transmission, and is a standard off-the-shelf starter
- High-torque starter included — American-built Powermaster 9000
- CNC precision-machined in the U.S.A. — adapter plate and crankshaft spacer machined from 6061 billet aluminum at our shop in Waunakee, Wisconsin
- Flexplate options available — use your own 164-tooth big block flexplate, or add one to your order in the balance your engine requires
- Hardware included — mounting hardware for adapter-to-block, transmission-to-adapter, starter, and backer plate installation
- US Shift controller packages available — save $125 on your Speed Gems adapter kit when you add a Quick 6 for a 6R80, or $100 when you add a Quick 4 for an AOD-E, 4R70W (wide ratio AOD-E), 4R75, E4OD or 4R100
- Throttle position signal (TPS) provisions are the customer's responsibility — check out US Shift's TPS kit options, or give us a call if you're not seeing what you need
Fitment
Engine
- Ford 429/460 big block family
- Not compatible with the Ford 351M or 400 — see kit FO2502 coming soon
Transmission
- 6R80 from a Modular V8 such as a 5.0L or 5.4L, from a 2011 or newer vehicle for an aftermarket controller to work
- 4R70W, 4R75W, 5R110, 4R100, and 6R140 (with V8 gas case)
- V6 and EcoBoost 6R80 transmissions will not work
Flexplate and Torque Converter
- Requires a 164-tooth Ford big block flexplate in the balance specific to your engine — use your own, or add one to your order
- 157-tooth and 184-tooth flexplates will not work
- Designed for the 4-stud converter found in most Modular V8-style transmissions
Which balance do you need? As a general guide, 1968–1979 big blocks were mostly internally balanced (0 oz), while 1980–1998 engines were mostly externally balanced (24 oz). Engines vary, so call us at (763) 767-4480 before ordering and we can help you confirm what yours requires, or whether your existing flexplate will work.
What's Included
- (1) Speed Gems adapter plate
- (1) Crankshaft spacer
- (1) Starter
- (1) Starter spacer
- (1) Backer plate and inspection cover
- Hardware required to install
Optional add-on: 164-tooth flexplate, available in the balance your engine requires.
About Our Big Block Ford Adapter Kit
Our FO2501 adapter kit gives the Ford 429/460 big block access to modern Ford overdrive automatics, pairing a proven engine with the gearing and efficiency of a 6R80 or 4R70W. Constructed from 100% USA-sourced materials and CNC precision-machined at our shop in Waunakee, Wisconsin, the 6061 billet aluminum adapter plate and crankshaft spacer keep alignment true and bolt up without cutting, grinding, or modification to any component.
Not sure this is the right kit? Matching adapter kits to your engine and transmission can be tricky. Call us at (763) 767-4480 before ordering — we're happy to confirm fitment. Speed Gems is not responsible for return shipping on mismatched kits.