Hi Steven,
First, I am thinking a .040 overbore in the thin wall casting 289 block very likely will be a hot temp running motor. Not sure I would want to go there, especially in a Tiger.
The CAT newsletters have two excellent, lengthy articles on the swap/adapter subject. I see you are not a member of CAT, but maybe you could join and work out something with Rick to get copies of those back issues.
But beyond just the trans issue is the domino effect. Does the 302 crank require a 50 oz. harmonic balancer? If so, additional cost there since your 260 has a 28 oz. Do you get a 302 flywheel that goes with the harmonic balancer weight? Also, the crank pulley has three mounting holes, and many 302 balancers are drilled for a four hole pulley. Need to get an aftermarket one drilled for both configurations. Again, extra costs.
As I recall, all the Ford bell housings that can be made to adapt go with a 164 tooth flywheel. (My Tiger Tales issues are on loan to a friend.) The stock Tiger one is a 157 tooth flywheel. If so, then there is also a need to get a clutch and pressure plate that will go with the bigger flywheel. I do know of people using a Quick Time scattershield with a 157 tooth flywheel, but they do not come cheap.
You would also need to get another clutch slave mounting bracket since they bolt on using the bell housing bolts. I think I spent about $89.00 on this part alone. The hole spacing is different between the 5 and 6 bolt bell housings.
The 6 bolt bell housings also have a bigger hole for the trans input shaft bearing retainer than the 5 bolt ones. So you need a larger retainer housing or machined spacer of some sort to take up the space. Either way, another expense.
Also, you will need a larger block plate for the 6 bolt block to bell housing interface.
If you are going to be running headers, and adapt a 6 bolt Ford bell housing, you may need to get a smaller, gear reduction starter versus using the stock one. The larger bell housing pushes the starter more outboard toward the exhaust system. The stock starter was a very tight fit with my stock 260 motor and bell housing and aftermarket headers as it was.
I probably left out something in all of this. As I said, there is a domino effect!
Gene
Oh and by the way, I did join CAT and have received newsletters. I have not been told that my membership has lapsed. I also thought you could not post on the Forum if not a member.
