SQL Server 2012 :: Increment Query Based On Two Tables?

I have two tables with this info:

TABLE 1

COL1 COL2 COL3
AAA BBB CCC
QQQ WWW EEE
AAA SSS DDD
WWW EEE RRR
BBB BBB BBB

TABLE 2

COL1 COL2 COL3 COL4
b b b 343
a a a 344
c c c 345
d d d 346
e e e 347

I want to insert TABLE 1 into TABLE 2 with a query that will auto increment to COL4 looking like this:

COL1 COL2 COL3 COL4
b b b 343
a a a 344
c c c 345
d d d 346
e e e 347
AAA BBB CCC 348
QQQ WWW EEE 349
AAA SSS DDD 350
WWW EEE RRR 351
BBB BBB BBB 352

I know this can be done easily by just altering the column to have an auto-increment datatype, but I currently cannot do that at this moment.