gas tank help

[howe2301]

Hey every have a few questions about my gas tank.

First i have a 16 gallon gas tank and was thinking of putting a 20 gallon tank in. i was looking at my LMC mag and the filler neck looks like the same part number and the straps look like the same part number. also the tank look to be the same except in length. so would it just go in or would i have to drill new holes for the straps to bolt into.

Second sometime in the next few years i would like to do a 5.3L/4L60 or 4L80 swap on it so thinking ahead (something i never do by the way) i was thinking of just putting in the 87 tank now. i dont think it well affect my carb fuel pump but if anyone knows for sure id like to know before i get the new tank.

thanks for any info.