3spd to 4spd swap help needed

[bueller60]

This is my first post so be kind. First of all, great site. I am the proud owner of a 68 Chevy stepside with a 250/3spd on the colunm. I can live with the 250 but the 3spd on the column is driving me nuts. I found a cheap 4spd (sm465) out of a 69 3/4 ton on Craigslist and made a deal. Once I got the tranny home, I started looking things over and now I need some help. Is this tranny going to bolt in? The 3spd has tranny mounts that attach to the bellhousing with no other crossmember. The 465 looks like it needs a regualr crossmember bolted more rearward?? If needed, I could go retrieve the crossmember from the parts truck. Also, I'm almost positive that my truck has a low hump floor. Does the 465 need more room or will it fit? Lastly, the 465 has a yoke with a U joint bracket attached....my 3 spd has the driveshaft slide into the rear of the tranny. Do I need a different driveshaft or ?? I could use some help from the experts. Thanks in advance.