http://www.chevellestuff.com/tech/autom ... nsions.htm http://www.tciauto.com/Products/TechInfo/trans_dims.asp http://grannys.tripod.com/transdim.html http://700r4.com/trans/comparrison.html http://www.drwtransmission.com/trans_weights.htm
https://www.transdepot.net/Automati...MI6pvahtXT2wIVDi5pCh1SCQ6BEAAYASAAEgJiXvD_BwE https://www.transdepot.net/ChevyGMGMC-Transmissions_ep_55-1.html http://www.nastyz28.com/chevy-transmission-identification.php http://garage.grumpysperformance.co...sion-and-oil-cooler-increases-durability.176/ http://garage.grumpysperformance.com/index.php?threads/remote-oil-filters.14755/#post-80757 http://garage.grumpysperformance.co...n-cooler-info-and-derale-trans-cool-pans.662/ http://garage.grumpysperformance.com/index.php?threads/oil-filters-related-info.2080/#post-54352 http://garage.grumpysperformance.com/index.php?threads/oil-system-mods-that-help.2187/#post-49790 http://garage.grumpysperformance.co...ers-and-oil-filter-clearance.4904/#post-13526 these threads and several links may help https://www.amsoil.com/AmsoilGarage/internal/vehiclelookuppage.aspx?zo=531421&page=appguide https://www.autozone.com/repairinfo...NameForTitle=Transmission+Fluid+Type/Capacity
The 200R4 & Turbo 400 Have exact Blueprint Trans mount pad location distance Grumpy. Difference is the TH400 Tailshaft extension housing length. Moot Minor obsticale to overcome. Will bolt right in place a TH400 To Replace the much weaker 200R4.
Looking at the Photo provided by You Grumpy the 200R4 has a wider case than a TH400. Will fit with room to spare a TH400.
The Trans tunnel in the 63 Pontiac Gp is Dinky. Flat floor design to give huge room sitting down. The Slim Jim Roto Hydromatic 1961-64 used in Catalina and Grand Prix. Weak trans. Just had to bump the floor for lower Bellhousing. Make my own crossmember from original. Fit right in the TH400.
Lower ears on the TH400 can be removed. I chose not too. To run a dust cover back then. Gain 2 -3 inches more room if lower ears cut off. I run no dust cover today. Not needed for Hotrodding.
The Torque Rating Chart Grumpy. 200R4 is Rated Low Torque Stock and Modified. Turbo 400 is Rated High Torque Stock and Modified. TH400 is the Winner. Till Funds are Acquired for 4L80E Overdrive.
https://m.ebay.com/itm/TH400-Turbo-...:~NgAAOSwspdaqqOq:sc:USPSPriority!61348!US!-1 Pretty good rebuild kit. Try and find the kit I bought.