Hope you've got a great deal on a World Class V8 trans.
Will it bolt up to your bellhousing as easily as the 4-cyl Non World Class conversions Al does?
The input shaft has a slightly larger diameter on a V8.
What are you doing clutch-wise?
My Aussie 200 1966 block can take a SBF bellhousing and clutch if
1. you use a blank steel flywheel for a manual 300 I6, and redrilled to a 2.75" bolt spacing, not the 3" bolt spacing standard on the SBF/240/300 family. This is a pest. Don't 'fill and drill' a cast flywheel, as it may explode and take your leg out.
2. For starter clearance, you need to grind the block with a die grinder as, unlike the later Aussie blocks, the US 200 has a thick flange holding the two wide bolts of the set of four.
3. and then make an Aussie-style adpator to suit. (Aussie adaptors are a term I've coined to mark the plate adaptor-type of 5/8" profile cut plate that Australians such as Rod Hatfield at Castlemaine Rod Shop pioneered for Aussie Hot Rodders fitting 5-speed gearboxes to Aussie and American V8's)
4. The stock V8 clutch is pretty good, and I'd be looking at that as an option.
Al has been own the road of many conversions, and feels for a stockish 200 with T5, the 4-cyl Mustang box with the stock 200 bell and clutch is best.
But with a 302 style 200 plus stampeading ponies under the hood, I'd be wanting some V8-style back-up.