Here's some stats on the number of East Indians in the Toronto area from 1991. Seems like they called them East Indians at the time, I'm assuming it's equivalent to South Asian which was not a category on the 1991 census. For the home language, I'm using to try to gauge how the different South Asian sub-groups are distributed.
Brampton: 14,950 (6.40%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 115 (400)
Gujurati: 810 (1,660)
Punjabi: 6,360 (9,795)
Urdu: 710 (2,255)
Hindi: 415 (4,620)
Markham: 9,185 (5.99%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 500 (830)
Gujurati: 1010 (2,495)
Punjabi: 980 (2,030)
Urdu: 405 (1,720)
Hindi: 520 (3,070)
Mississauga: 27,235 (5.90%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 1,535 (2,615)
Gujurati: 1,045 (2,810)
Punjabi: 9,045 (14,635)
Urdu: 1,905 (5,475)
Hindi: 970 (8,200)
Scarborough: 26,960 (5.18%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 7,280 (11,035)
Gujurati: 3,505 (6,665)
Punjabi: 2,290 (4,510)
Urdu: 2,215 (5,225)
Hindi: 1,060 (7,685)
East York: 4,720 (4.63%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 700 (900)
Gujurati: 1,380 (2,820)
Punjabi: 145 (385)
Urdu: 290 (1,115)
Hindi: 120 (970)
Etobicoke: 13,540 (4.40%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 845 (1,320)
Gujurati: 1,005 (1,870)
Punjabi: 5,325 (7,610)
Urdu: 675 (2,125)
Hindi: 625 (4,190)
North York: 20,160 (3.61%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 2,890 (4,485)
Gujurati: 2,125 (4,735)
Punjabi: 4,525 (6,955)
Urdu: 1,400 (3,875)
Hindi: 1,010 (6,650)
Vaughan: 3,920 (3.53%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 20 (90)
Gujurati: 510 (1,095)
Punjabi: 480 (1,045)
Urdu: 180 (385)
Hindi: 170 (1,305)
Ajax: 1,670 (2.82%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 20 (75)
Gujurati: 55 (205)
Punjabi: 185 (400)
Urdu: 15 (245)
Hindi: 0 (430)
Pickering: 1,675 (2.45%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 0 (60)
Gujurati: 215 (330)
Punjabi: 70 (335)
Urdu: 140 (615)
Hindi: 65 (370)
Richmond Hill: 1,935 (2.42%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 0 (65)
Gujurati: 155 (455)
Punjabi: 75 (355)
Urdu: 55 (340)
Hindi: 230 (675)
Oakville: 2,480 (2.18%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 10 (50)
Gujurati: 70 (325)
Punjabi: 575 (1,315)
Urdu: 95 (395)
Hindi: 55 (775)
York: 2,505 (1.80%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 650 (900)
Gujurati: 155 (340)
Punjabi: 400 (660)
Urdu: 245 (680)
Hindi: 120 (665)
Old Toronto: 9,255 (1.47%)
Home languages that are native to South Asia* (population with knowledge of language in brackets)
Tamil: 3,635 (4,845)
Gujurati: 880 (1,740)
Punjabi: 1,150 (1,935)
Urdu: 775 (2,520)
Hindi: 355 (2,975)
*other South Asian languages would just have been lumped under "other" which would include non-South Asian languages too. Most notable, there's no data for Bengali speakers.
Some South Asians might know how to speak their ancestral language but no longer speak it at home, others might have knowledge of multiple South Asian based languages.
Looks like Tamils were mostly based in Central Toronto and Scarborough while the Punjabis were already fairly suburbanized into Brampton and Mississauga/Etobicoke (presumably in large part in Malton/Rexdale). However, even for all East Indians, it looks like they were already relatively suburbanized in 1991 since Old Toronto had a lower % than most suburbs. All the above suburbs had higher percentages, including Oakville which I didn't expect, as did Whitby (but didn't bother including it since it has <1000 East Indians). It's only the really far flung suburbs like Newmarket, Oshawa and Milton that had lower percentages of South Asians than Old Toronto. It looks like the more outlying suburbs of Durham, York and Halton had more established/assimilated East Indians since the % of them that speaks one of those 5 languages at home is smaller.
So patterns were already somewhat similar to today - Tamils/Sri Lankans in the East, Punjabis/Sikhs in the NE, Pakistanis (Urdu) in Mississauga and Scarborough (I think they're more numerous in Sauga vs Scarb now though) and other South Asians (Hindi/Gujurati) kind of all over.